In advance: I don't know if this feature already exists in newer versions. I'm still using Avidemux 2.8.2 241214 build - the last that works Windows 7 ( :'( ) but if I ever change my system this feature would be veeeery handy: when you select part of video (with start and stop markers) it would be nice if the playback would stop at the end marker. It could be an additional option in settings.