This would be great to have in standard view as well, then I wouldn't have to close and reopen my MC server running on my Raspberry Pi every time I add new audio files.
I think there already is a "sync changes with library server" button in standard view, it's in the library manager view of the server library. That seems to do exactly what folks in this thread want. The only issue with it is that it blocks the interface, and sometimes takes quite a while on larger libraries (sometimes twenty to thirty seconds or so), so I rarely use it and just wait for the background sync. As an example if there have been no changes between client and server it returns pretty quickly, but if I've even played two or three songs it takes five or six seconds to return, and that only increases as changes pile up. This is with all clients and servers wired into the same ethernet network, and a library with ~110,000 items, so others might have a different experience with a different network or a smaller or larger library.
It would still be nice to be able to put the button on the task bar or in theater view. If a more portable button does get implemented, if it could not block that would be awesome!