I've been working on the Stylized 3d Forest but now I have all of these presets and I can't figure out how to get rid of them.
Hi Wendy,
They are stored in a bit weird place (not where the Built-in Presets are), but (and I assume you are still using Mint) here's where they are on Linux:
There you can simply Delete them :)
(You might need to enable 'Show Hidden Files' in your Home folder, or just use the Terminal.)
BTW: if you know the name of one of those presets, you can use 'locate' to see where it is stored (you already know it now, but it's a very handy command), for instance:
It even finds it when you just type newtree without the .py.