Allowing #define DELTA_TOWER_ANGLE_TRIM[C_AXIS]

More consistent with M665 where C-value is allowed as well, then
normalized

Marlin/Conditionals_post.h

       #define DELTA_ENDSTOP_ADJ { 0.0, 0.0, 0.0 }
     #endif
     #ifndef DELTA_TOWER_ANGLE_TRIM
-      #define DELTA_TOWER_ANGLE_TRIM {0.0, 0.0}
+      #define DELTA_TOWER_ANGLE_TRIM {0.0, 0.0, 0.0}
     #endif
     #ifndef DELTA_RADIUS_TRIM_TOWER
       #define DELTA_RADIUS_TRIM_TOWER {0.0, 0.0, 0.0}

Marlin/Marlin_main.cpp

     if (code_seen('X')) delta_tower_angle_trim[A_AXIS] = code_value_linear_units();
     if (code_seen('Y')) delta_tower_angle_trim[B_AXIS] = code_value_linear_units();
     if (code_seen('Z')) { // rotate all 3 axis for Z = 0
-      delta_tower_angle_trim[A_AXIS] += code_value_linear_units();
-      delta_tower_angle_trim[B_AXIS] = code_value_linear_units();
+      delta_tower_angle_trim[A_AXIS] -= code_value_linear_units();
+      delta_tower_angle_trim[B_AXIS] -= code_value_linear_units();
     }
     recalc_delta_settings(delta_radius, delta_diagonal_rod);
   }

Marlin/configuration_store.cpp

 
   #if ENABLED(DELTA)
     const float adj[ABC] = DELTA_ENDSTOP_ADJ,
-                dta[2] = DELTA_TOWER_ANGLE_TRIM;
+                dta[3] = DELTA_TOWER_ANGLE_TRIM;
     COPY(endstop_adj, adj);
     delta_radius = DELTA_RADIUS;
     delta_diagonal_rod = DELTA_DIAGONAL_ROD;
     delta_segments_per_second = DELTA_SEGMENTS_PER_SECOND;
     delta_calibration_radius = DELTA_CALIBRATION_RADIUS;
-    COPY(delta_tower_angle_trim, dta);
+    delta_tower_angle_trim[A_AXIS] = dta[A_AXIS] - dta[C_AXIS];
+    delta_tower_angle_trim[B_AXIS] = dta[B_AXIS] - dta[C_AXIS];
     home_offset[Z_AXIS] = 0;
 
   #elif ENABLED(Z_DUAL_ENDSTOPS)

Marlin/example_configurations/delta/FLSUN/auto_calibrate/Configuration.h

   // Trim adjustments for individual towers
   // tower angle corrections for X and Y tower / rotate XYZ so Z tower angle = 0
   // measured in degrees anticlockwise looking from above the printer
-  #define DELTA_TOWER_ANGLE_TRIM { -0.00, -0.00 } // get these from auto calibrate
+  #define DELTA_TOWER_ANGLE_TRIM { 0.00, 0.00, 0.00 } // get these from auto calibrate
 
   // delta radius and diaginal rod adjustments measured in mm
   //#define DELTA_RADIUS_TRIM_TOWER {0.0, 0.0, 0.0}

Marlin/example_configurations/delta/FLSUN/kossel_mini/Configuration.h

   // Trim adjustments for individual towers
   // tower angle corrections for X and Y tower / rotate XYZ so Z tower angle = 0
   // measured in degrees anticlockwise looking from above the printer
-  #define DELTA_TOWER_ANGLE_TRIM { -0.00, -0.00 } // get these from auto calibrate
+  #define DELTA_TOWER_ANGLE_TRIM { 0.00, 0.00, 0.00 } // get these from auto calibrate
 
   // delta radius and diaginal rod adjustments measured in mm
   //#define DELTA_RADIUS_TRIM_TOWER {0.0, 0.0, 0.0}

Marlin/example_configurations/delta/generic/Configuration.h

   // Trim adjustments for individual towers
   // tower angle corrections for X and Y tower / rotate XYZ so Z tower angle = 0
   // measured in degrees anticlockwise looking from above the printer
-  #define DELTA_TOWER_ANGLE_TRIM { -0.00, -0.00 } // get these from auto calibrate
+  #define DELTA_TOWER_ANGLE_TRIM { 0.00, 0.00, 0.00 } // get these from auto calibrate
 
   // delta radius and diaginal rod adjustments measured in mm
   //#define DELTA_RADIUS_TRIM_TOWER {0.0, 0.0, 0.0}

Marlin/example_configurations/delta/kossel_mini/Configuration.h

   // Trim adjustments for individual towers
   // tower angle corrections for X and Y tower / rotate XYZ so Z tower angle = 0
   // measured in degrees anticlockwise looking from above the printer
-  #define DELTA_TOWER_ANGLE_TRIM { -0.00, -0.00 } // get these from auto calibrate
+  #define DELTA_TOWER_ANGLE_TRIM { 0.00, 0.00, 0.00 } // get these from auto calibrate
 
   // delta radius and diaginal rod adjustments measured in mm
   //#define DELTA_RADIUS_TRIM_TOWER {0.0, 0.0, 0.0}

Marlin/example_configurations/delta/kossel_pro/Configuration.h

   // Trim adjustments for individual towers
   // tower angle corrections for X and Y tower / rotate XYZ so Z tower angle = 0
   // measured in degrees anticlockwise looking from above the printer
-  #define DELTA_TOWER_ANGLE_TRIM { -0.00, -0.00 } // get these from auto calibrate
+  #define DELTA_TOWER_ANGLE_TRIM { 0.00, 0.00, 0.00 } // get these from auto calibrate
 
   // delta radius and diaginal rod adjustments measured in mm
   //#define DELTA_RADIUS_TRIM_TOWER {0.0, 0.0, 0.0}

Marlin/example_configurations/delta/kossel_xl/Configuration.h

   // Trim adjustments for individual towers
   // tower angle corrections for X and Y tower / rotate XYZ so Z tower angle = 0
   // measured in degrees anticlockwise looking from above the printer
-  #define DELTA_TOWER_ANGLE_TRIM { -0.00, -0.00 } // get these from auto calibrate
+  #define DELTA_TOWER_ANGLE_TRIM { 0.00, 0.00, 0.00 } // get these from auto calibrate
 
   // delta radius and diaginal rod adjustments measured in mm
   //#define DELTA_RADIUS_TRIM_TOWER {0.0, 0.0, 0.0}