Today, I downloaded the current Eclipse programming IDE, and tried to right-click the Eclipse.exe and do Pin to Start. It did not do that, nothing showed up in my start menu. Then I did the same operation using Windows File Explorer, right click then Pin to Start, and File Explorer successfully accomplished this. Now I have an icon, I can resize to small and put where I want it. Please fix this in Dopus, as I wasted some time fiddling around trying to get it to work here.
It doesn't work in any process except explorer.exe; not even other Microsoft processes. Try it from Notepad's File > Open dialog, for example.
It's a bug in Windows. (Even if it's intentional, to block software from changing the Start Menu, they shouldn't show the menu item in other processes if it won't work.)
Lots of forum threads about this already if you search.
Actually, which Opus version are you using? After some digging, we found a workaround for this a few years ago, and it still seems to work here at least.
It can depend on the location and type of item being pinned, from what I remember (but the same is true in File Explorer).
Edit: It's working on one Win 11 machine but not on another Win 10 one, although it has worked on Win 10 in the past. (Also doesn't work in Notepad on the same Win 10 machine.) Seems that Microsoft keep breaking/fixing/breaking it. It's not really in our control.
Maybe this can help somewhat (check the comments there): Pin any executable to Start