It tripped me up too initially, but they added a nice workaround to it so one doesn't need to disable the deleting cookies completely.

On the pages where you want to stay logged in like in HN, click the lock icon left of the URL and toggle "LibreWolf: Always store cookies/data for this site" and that's it.

There's certainly something refreshing about knowing exactly for which sites I'm storing cookies (so far kagi, HN, gmail, YT...)