In mkvtoonix GUI v54.0.0 64bit, in multiplexer section, when i want to multiplex a video file with an audio file, i open both files (video and audio) choose all the option i'm interested in, then add it to the queue and finally i press Ctrl+w to close the tab. But when i do that a second time at the end Ctrl+w doesn't close the tab. The only way to make ctrl+w work again is to click on one of the choice on the left (info tool, header editor, chapter editor ...) and then come back to multiplexer. No change on my pc betwen this version and the previous one in whitch it was working fine. I hope someone will understand the problem, english is not my first language.