Use a default monitor_speed of 250000

platformio.ini

 # Globally defined properties
 # inherited by all environments
 [env]
-framework   = arduino
-build_flags = ${common.build_flags}
-lib_deps    = ${common.lib_deps}
+framework     = arduino
+build_flags   = ${common.build_flags}
+lib_deps      = ${common.lib_deps}
+monitor_speed = 250000
 
 #################################
 #                               #
 lib_deps          = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed     = 250000
 
 #
 # ATmega1280
 lib_deps          = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed     = 250000
 
 #
 # RAMBo
 lib_deps          = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed     = 250000
 
 #
 # FYSETC F6 V1.3
 lib_deps          = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed     = 250000
 
 #
 # Sanguinololu (ATmega644p)
 lib_deps      = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed = 250000
 
 #
 # Sanguinololu (ATmega1284p)
 lib_deps      = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed = 250000
 
 #
 # Melzi and clones (ATmega1284p)
 lib_deps      = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed = 250000
 build_flags   = ${common.build_flags}
 lib_ignore    = TMCStepper
 upload_speed  = 57600
 lib_deps      = ${common.lib_deps}
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed = 250000
 build_flags   = ${common.build_flags}
 lib_ignore    = TMCStepper
 upload_speed  = 115200
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 lib_ignore    = TMCStepper
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed = 250000
 
 #
 # AT90USB1286 boards using DFU bootloader
 lib_deps      = ${common.lib_deps}
 lib_ignore    = TMCStepper
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_AVR>
-monitor_speed = 250000
 
 #
 # Due (Atmel SAM3X8E ARM Cortex-M3)
 platform      = atmelsam
 board         = due
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_DUE>
-monitor_speed = 250000
 
 [env:DUE_USB]
 platform      = atmelsam
 board         = dueUSB
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_DUE>
-monitor_speed = 250000
 
 [env:DUE_debug]
 # Used when WATCHDOG_RESET_MANUAL is enabled
 platform      = atmelsam
 board         = due
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_DUE>
-monitor_speed = 250000
 build_flags   = ${common.build_flags}
   -funwind-tables
   -mpoke-function-name
 lib_compat_mode   = strict
 extra_scripts     = Marlin/src/HAL/HAL_LPC1768/upload_extra_script.py
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_LPC1768>
-monitor_speed     = 250000
 lib_deps          = Servo
   LiquidCrystal
   U8glib-HAL=https://github.com/MarlinFirmware/U8glib-HAL/archive/bugfix.zip
 lib_compat_mode   = strict
 extra_scripts     = Marlin/src/HAL/HAL_LPC1768/upload_extra_script.py
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_LPC1768>
-monitor_speed     = 250000
 lib_deps          = Servo
   LiquidCrystal
   U8glib-HAL=https://github.com/MarlinFirmware/U8glib-HAL/archive/bugfix.zip
 lib_ldf_mode      = chain
 debug_tool        = stlink
 upload_protocol   = serial
-monitor_speed     = 250000
 
 #
 # BigTree SKR Mini V1.1 / SKR mini E3 / SKR E3 DIP (STM32F103RCT6 ARM Cortex-M3)
 build_flags   = ${common.build_flags} -DUSE_STM32GENERIC -DSTM32GENERIC -DSTM32F4 -DMENU_USB_SERIAL -DMENU_SERIAL=SerialUSB -DHAL_IWDG_MODULE_ENABLED
 lib_ignore    = Adafruit NeoPixel, TMCStepper
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32_F4_F7> -<src/HAL/HAL_STM32_F4_F7/STM32F7>
-monitor_speed = 250000
 
 #
 # STM32F7 with STM32GENERIC
 build_flags   = ${common.build_flags} -DUSE_STM32GENERIC -DSTM32GENERIC -DSTM32F7 -DMENU_USB_SERIAL -DMENU_SERIAL=SerialUSB -DHAL_IWDG_MODULE_ENABLED
 lib_ignore    = Adafruit NeoPixel, TMCStepper
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32_F4_F7> -<src/HAL/HAL_STM32_F4_F7/STM32F4>
-monitor_speed = 250000
 
 #
 # ARMED (STM32)
   -IMarlin/src/HAL/HAL_STM32
 lib_ignore    = Adafruit NeoPixel, SoftwareSerial
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32>
-monitor_speed = 250000
 
 #
 # Longer 3D board in Alfawise U20 (STM32F103VET6)
 extra_scripts = buildroot/share/PlatformIO/scripts/STM32F103VE_longer.py
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
 lib_ignore    = Adafruit NeoPixel, LiquidTWI2, SPI
-monitor_speed = 250000
 
 #
 # MKS Robin (STM32F103ZET6)
 extra_scripts = buildroot/share/PlatformIO/scripts/mks_robin.py
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
 lib_ignore    = Adafruit NeoPixel, SPI
-monitor_speed = 250000
 
 
 #
 extra_scripts = buildroot/share/PlatformIO/scripts/mks_robin_lite.py
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
 lib_ignore    = Adafruit NeoPixel, SPI
-monitor_speed = 250000
 
 #
 # MKS ROBIN LITE3 (STM32F103RCT6)
 extra_scripts = buildroot/share/PlatformIO/scripts/mks_robin_mini.py
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
 lib_ignore    = Adafruit NeoPixel, SPI
-monitor_speed = 250000
 
 #
 # MKS Robin Nano (STM32F103VET6)
 extra_scripts = buildroot/share/PlatformIO/scripts/mks_robin_nano.py
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
 lib_ignore    = Adafruit NeoPixel, SPI
-monitor_speed = 250000
 
 #
 # JGAurora A5S A1 (STM32F103ZET6)
 extra_scripts = buildroot/share/PlatformIO/scripts/jgaurora_a5s_a1_with_bootloader.py
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
 lib_ignore    = Adafruit NeoPixel, SPI
-monitor_speed = 250000
 
 #
 # Malyan M200 (STM32F103CB)
 extra_scripts = buildroot/share/PlatformIO/scripts/chitu_crypt.py
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
 lib_ignore    = Adafruit NeoPixel
-monitor_speed = 250000
 
 #
 # STM32F401VE
   buildroot/share/PlatformIO/scripts/STEVAL__F401XX.py
 lib_ignore        = Adafruit NeoPixel, TMCStepper, SailfishLCD, SailfishRGB_LED, SlowSoftI2CMaster, SoftwareSerial
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_STM32>
-monitor_speed     = 250000
 
 #
 # FLYF407ZG
 extra_scripts     = pre:buildroot/share/PlatformIO/scripts/generic_create_variant.py
 lib_ignore        = Adafruit NeoPixel, TMCStepper, SailfishLCD, SailfishRGB_LED, SlowSoftI2CMaster, SoftwareSerial
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_STM32>
-monitor_speed     = 250000
 
 
 #
 debug_tool        = stlink
 #upload_protocol   = stlink
 upload_protocol   = serial
-monitor_speed     = 250000
 
 #
 # STM32F407VET6 with RAMPS-like shield
 extra_scripts     = pre:buildroot/share/PlatformIO/scripts/generic_create_variant.py
 lib_ignore        = Adafruit NeoPixel, TMCStepper, SailfishLCD, SailfishRGB_LED, SlowSoftI2CMaster, SoftwareSerial
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_STM32>
-monitor_speed     = 250000
 
 #
 # BigTreeTech SKR Pro (STM32F407ZGT6 ARM Cortex-M4)
   Arduino-L6470=https://github.com/ameyer/Arduino-L6470/archive/dev.zip
 lib_ignore        = SoftwareSerial, SoftwareSerialM
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_STM32>
-monitor_speed     = 250000
 
 #
 # BigTreeTech BTT002 (STM32F407VET6 ARM Cortex-M4)
 extra_scripts     = pre:buildroot/share/PlatformIO/scripts/generic_create_variant.py
 lib_ignore        = Adafruit NeoPixel, SailfishLCD, SailfishRGB_LED, SlowSoftI2CMaster
 src_filter        = ${common.default_src_filter} +<src/HAL/HAL_STM32>
-monitor_speed     = 250000
 
 #
 # Teensy 3.1 / 3.2 (ARM Cortex-M4)
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 lib_ignore    = Adafruit NeoPixel
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_TEENSY31_32>
-monitor_speed = 250000
 
 #
 # Teensy 3.5 / 3.6 (ARM Cortex-M4)
   TMC26XStepper=https://github.com/trinamic/TMC26XStepper/archive/master.zip
 lib_ignore    = Adafruit NeoPixel
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_TEENSY35_36>
-monitor_speed = 250000
 
 #
 # Espressif ESP32
 lib_ignore    = LiquidCrystal, LiquidTWI2, SailfishLCD, SailfishRGB_LED
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_ESP32>
 upload_speed  = 115200
-monitor_speed = 250000
 #upload_port   = marlinesp.local
 #board_build.flash_mode = qio
 
   -Os
 lib_ignore    = Adafruit NeoPixel
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32> +<src/HAL/HAL_STM32_F4_F7> -<src/HAL/HAL_STM32_F4_F7/STM32F7>
-monitor_speed = 250000
 upload_protocol = dfu
 
 #