Marlin 2.1.2 output and planner

Hi everyone, I'm working on a change to firmware 2.1.2. I am using an Arduino Mega 2560 board configured in the firmware as BOARD_MEGATRONICS_3 in configuration.h. The goal of my modification is to obtain a signal in pin 46 of the board every time a movement command is executed. I made a first attempt by inserting this part of code into the planner.cpp file.  This change was already done in a previous firmware version (not sure which one it is) using the planner.h file.  The 'old' modification worked correctly, the one I made works on the output side, emits the signal if a movement command is executed, the problem I encountered is an extreme slowdown in the final part of the machine's movements, more specifically when executing the home command for each axis makes a first part of the movement at normal speed and the final approach is very slow, making less than one step per second. I am studying how planner.cpp works and in general how Marlin works, so any type of documentation in any form is welcome, especially tutorials to understand the metalanguage in which Marlin is written, I am a beginner nothing is obvious for me. If someone has already made this type of modification and it works on this version (2.1.2) I would be very grateful if you explained to me how you did it. For any further details that are deemed useful do not hesitate to ask. I attach the configuration.h , configuration_adv.h and planner.cpp files (.txt) if they can be useful. [Configuration.txt](https://github.com/user-attachments/files/18628096/Configuration.txt) [Configuration_adv.txt](https://github.com/user-attachments/files/18628097/Configuration_adv.txt) [planner.txt](https://github.com/user-attachments/files/18628098/planner.txt) Many thanks in advance to anyone who will answer.