Go ahead and do that then. uv is not preventing you from putting 10 projects within one folder.

It is still benefitial to not install stuff system wide, since this makes it easy to forget which stuff you already have installed and which is a missing dependency.

Keeping track of dependencies is kind part of a programers work, so as long as you're writing these things mostly for yourself do whatever you like. And I say that as someone who treats everything like a project that I will forget about in 3 days and need to deploy on some server a year later.