itunes (Catalina) synch with iphone 4

How do I synch my iPhone 4 with iTunes ? It seems I can't synch it in iTunes anymore but iPhone 4 appears in Finder... very annoying. In Finder it only shows the songs but I don't see what playlists are currently on my iPhone.. I don't dare to say yes to synch because it's set to "whole library" which I don't want on my iPhone... I only want selected playlists... I want to keep what's already on my iPhone and add a new playlist. Photo attached. I dragged the new playlist to iPhone 4 and it seems to be on the phone now... but why can't I see all my phone's playlists on the computer?