I just installed MP3 Tag v2.95 in Windows 10. MP3 Tag doesn't appear in the Start menu. I right-clicked the .exe file in File Explorer and clicked Pin to Start, but it still doesn't appear. I can launch it by double-clicking on the .exe file, so I assume it got installed correctly.
If you select the portable installation then it leaves no traces on your system so you have to do it all manually.
You could try to reinistall it with the standard installation.
MP3tag does not appear in the quick start bar, unless you add it after the first start.
Unless it's a default that I didn't see, I didn't select portable. I'm not trying to get it in the quick start bar, I'm trying to get it to appear when I click the Start button and see a list of all installed programs.
As MP3tag installs without any problems in thousands of cases, I strongly suspect that the cause for your observation is something local.
But I cannot look over your shoulder.
The easiest way would be to try another installation with the careful observation of all options.