Interesting advice from Nidhogg. I am really a linux user where I use a fontmanager but I will have a look at that in my Win10 (VM) otherwise:
For those fonts that come already installed in Windows:
Win10 can Hide/Show fonts, but unfortunately Gimp will still see them. Gimp is developed in linux where font handling is a bit different.

What you can do is use the
tag function. see:
https://docs.gimp.org/2.10/en/gimp-tagging.htmlYou have to use the Fonts dock. If that is not there add it. Windows -> Dockable Dialogues -> Fonts.

1. There is a drop down for filters (initially empty)
2. Any font (or selection of fonts - see the docs) can be given a tag. Different styles can be given any tag that makes sense to you. Handwriting, Gothic...anything.

3. Choosing a tag in the filter, shows matching fonts.
New fonts of course, should be added to the Gimp fonts folder.
If just for occasional use, no need a font manager, Store your fonts somewhere, use a file manager, copy into the Gimp folder and refresh the fonts (bottom of the fonts dock)