There are several websites I use daily, where I'd like to either remove certain elements (e.g. a sidebar I don't ever use), or change them to make it more usable (e.g. add position: sticky to a navbar).

I found a similar question that got answers with "Permanent Remover" and "Element Hiding Helper", but those aren't Quantum-Ready. One person also mentioned building his own scripts for this kind of thing. If there isn't that kind of addon, could you point me to a small example script that runs on each site load, so I have a starting point?