Back in my days on Reddit, my favourite feature was the ability to hide individual posts if I had downvoted them. It made it easy to hide things which I didn't want to see or felt shouldn't be seen
FYI, if you go to "Account Settings" and uncheck "Show Read Posts", this should automatically hide all posts that you open, up vote, or down vote.
I understand and agree though that having the ability to split that into separate options would be nice. But this might help you until they possibly add that option later. This is also tied to your account and not just the app, which is nice if you use Lemmy from multiple devices.
Currently though, I and several others are having issues where the last update appears to have broken that feature. I'm not sure if the issue is instance specific, (lemm.ee) or more broad.