ugfx_2.7\drivers\multiple\Win32\gdisp_lld_Win32.c
Only this file fits your description. In this there is function
void gfxEmulatorMouseInject(GDisplay *g, uint16_t buttons, coord_t x, coord_t y)
But don't example how to use it. In particular how to get GDisplay*g in main. And there is no use of a timer.
For example in STEmWin there are function
GUI_PID_STATE ts_state = {TSC_data.x, TSC_data.y, TSC_data.touchState, LAYER_0};
GUI_TOUCH_StoreStateEx(&ts_state);
simple and understandable
When this function is called, the GUI react