When I mark 2 subtitles called x_track4.srt and x_track5.srt and drag them to a movie in mkvtoolnix GUI, so x_track5 seems to be a sub of x_track4 and is not merged.
When I do the same with x_track4.srt and x_track6.srt it works fine.
If difference of the numbers is greater than 1 or or the second has another name than first, no problem…
Welcome!
That’s a feature that can be turned off in the preferences for situations where you have one logical file chopped up into many consecutively named ones which should all be played one after the other. You’ll find it in the preferences → “Multiplexer” → “Detect file name sequences…”
Thanks, it works fine now.