Hi Anatoliy,
The "Actions" after Stop can be configured on the Tool Setup | M0-M30 Page without any need to change KMotionCNC. You must have Test Version 4.33k. See:
Unfortunately KMotionCNC is a Microsoft MFC Application and fairly difficult to change. You will need to study MFC first and then ask specific questions. Troy has made some nice documents. See his posts. To add an entirely new Dialog window requires many steps including deriving a new CDialog Class.
Regards
TK