I haven't tested it fully, but the old workaround should still work(might need to start with a fresh sandbox folder for it to work) from what I'm seeing on one of the test pc I used back then.
Open MeguIVit, go to Options-> Settings, click the External Program Settings tab, click the ... button next to neroAacEnc, erase neroAacEnc.exe and select Any executable on the right, navigate to C:\meguIV which is a virtual folder that's not actually on your hard drive and go to the file(s) you want to update which is located to C:\meguIV\MeGUI\tools\mkvmerge in your case. Then
drag and drop copy-paste the new ones in there and hit cancel when you're done. Can be finicky but should work.
I'll try to test it and also make an updated version soon, but not sure when that'll be.
BTW, I don't know if the meguivit mod can handle mkv as a source, there might be information it can't get from the container since I don't know if vitreous made it able to handle those.
Edit: Both method of updating files still work, but the path in the sandbox folder changed a bit. It's this now(using x264 as an example):
Code:
Sandbox\MeguIVit\1.0.0.0\roaming\modified\@SYSDRIVE@\meguIV\MeGUI\tools\x264
Edit2: If you're using the sandbox file update method, you'll need to either create the path manually the first time(@SYSDRIVE@ is the same as C: in the dialog box so use those path from there) before copying the file or you can trigger the modified flag for the file you want to replace by renaming it in the dialog box(I'd also rename it back to the original name once that's done to make sure you don't forget it, the modified flag will stay even if it's back to its original name). Just make sure the file you replace it with has the original name from the dialog box in case the newer version is different.