When I right click a file or folder and select Mp2Tag in Total Commander (TC) Mp3tag opens background (behind) TC. If I use Explorer Mp3tag opens in the foreground.
I realize this could be something TC is doing but it doesn't do this with other programs I use.
I think I found a way to let TC change the calling process to be the foreground window via a call to AllowSetForegroundWindow from the shell extension.
I'll experiment a little and if everything works as intended, it'll be part of the next release. I'll keep you posted.
I've just released Mp3tag v3.30a, which should now allow Total Commander (and other 3rd-party file managers) to set the Mp3tag window as foreground window when launched via the context menu shell extension.
Please try it out and let me know if it works for you.