Editing an .ass in an mkv???? (Mac)

Is there a software for extracting and/or editing an .ass in an mkv (on mac) apart mkvtoolnix, where you dont get at the actual .ass in the mkv, but have to assign a new one (at least, as I understand it)???

Hi,
Aegisub is available for mac, and you can load the mkv into aegisub, and edit the ass.

Just downloaded and tried it. It lets me edit the script, but I only can save the edited script seperately. I have to mux it in into a new file with mkvtoolnix/MkvMerge.

Did I miss a button in Aegisub?

Else this works for my well enough Cheers!

Can't you edit the subs, and then save it by control+s?

If I do that, it does the 'save as', for the script only. Could be a hardware-thing, the laptop is getting old.
Aegisub does funny things, when I try to open a video: It opens it and lets the mouse pointer vanish. I can make it reappear for the next click, but I dont think, it is supposed to act like a weird mouse-vanishing field spell . Tomorrow I try a reinstall, just in case. Sometimes this helps.