I contacted support regarding the location of the sync button, and the sync progress bar indicator.
This is the reply I got:
EndNote 20 has some interface changes when compared to its previous versions and some of the options/panels have been removed in order to simplify the application Please feel free to write back if you have any further queries and I will be glad to assist you further.
I think it’s obvious from the comments here that we don’t want or need simplicity, we want functionality.
At the moment in version 20, if I want to click the sync button (which used to be just in the main screen), I have to go to Sync Status, wait until it retrieves the status, and then click it again, and I can’t do anything until it’s done.
This is much less functional than in version 19, where I just had a button, I click it, and it’s syncing in the background.
The other thing is that there used to be a small progress bar at the bottom of the screen showing how is sync going. This is now gone. The only way to see sync progress is by going to Sync Status, with it associated problems outlined above.
So in short: bring back the sync button, bring back the sync progress bar.