How to reference .tlc files

In my C2000 Blockset project I want to add custom backgroundTask() function inside the while(1){} loop. Modifying just the codetarget_file_process.tlc file is not enough to do that as this file in turn calls codertarget_mainwithoutOS.tlc where the ert_main.c file contents are created. I modified the codertarget_mainwithoutOS.tlc file to do what I need, but if I move the file from the location where it was installed (C:\Program Files\MATLAB\R2024b\toolbox\target\codertarget\rtw\codertarget_mainwithoutOS.tlc) to the folder inside my project it is no longer being copied to the \codegen\<project>\tlc folder and it is not found during build process.

How should I make sure the modified codertarget_mainwithoutOS.tlc is part of my project and is used to generate the code?