Baby Steps... baby steps beyond the average ffmpeg video converter towards a video editing app. It is **maybe** marginally better than combining clips in the average converter, but you should be using a real video editor to do that sort of thing anyway. There are plenty available free.
AnyMP4 Video Editor adds the program's folder, a folder in ProgramData, & a folder in Users\ [UserName]\ AppData\ Local\, along with 1 registry key for AnyMp4, & 1 registry key for uninstall.