Extensions for freeing up RAM

In Chrom*, I suggest "(Better-)OneTab".

In Firefox, I suggest "Tabs Aside".

OneTab: GitHub - cnwangjie/better-onetab: A better OneTab for Chrome (Temporarily removed from firefox & without maintain in a period & any cooperative purpose are welcome)

Tabs Aside: GitHub - tim-we/tabs-aside: A session/tab manager web extension for Firefox based on the Microsoft Edge feature.

How they work: you add tabs to a list to save them for later, without bookmarking them and subsequently forgetting them. (Better-)OneTab is more feature filled, but temporarily doesn't work for firefox.