The question is the following, sometimes the connected libraries, creating a directory along the path .pio/libdeps/, create examples of use.
And very often these are the usual *ino files for the Arduino IDE environment.
Previously, I simply copied the contents of the *ino file to the main.cpp file, which is located in the /src folder, moved all the functions above the setup(){} section and compiled the code.
Sometimes I had to copy some *h or *cpp header files next to the main.cpp.
But this is terribly inconvenient when there is code in the /examples folder.
And I am sure that there is some solution to compile the code from these folders.
Unfortunately, I am not experienced enough in configuring the platformio in this way
build_src_filter = +<.pio/libdeps/ROUND_DISPLAY_GFX/GFX Library for Arduino/examples/LVGL/LVGL_Arduino_v9/LVGL_Arduino_v9.ino>
If anyone knows a solution to my problem, please help.