I’ve been trying to find a way to disable or hide unused fonts in LibreOffice v24. The current list of fonts when in Writer is quite long. I’ve tried all the methods in FontBook, however right-click always seems to show “disable” greyed out. Also font files cannot be deleted or renamed because of permissions. I have also made up a custom group and and successfully copied files into the group. Writer doesn’t seem to allow groups to be selected. Therefore my drop down font list remains with all fonts shown. Can hiding or disabling unused fonts be done at all in MacOS Sequoia at all?
LibreOffice doesn’t manage fonts; it lists what the operating system offers. You must use a font manager to manage fonts.
If you cannot deactivate a font, it might be because it is a system font, see Remove, deactivate or activate fonts in Font Book on Mac – Apple Support (UK)
[Edit]
I don’t usually look at the font list unless I am selecting fonts for a document. Once I have chosen my selected fonts I modify the paragraph styles (and sometimes character styles) to use them in my document. After that I write without considering the fonts again, just choosing the relevant heading style or other paragraph style uses the selected font.
If later, I find I need a change of font, I can modify the styles (probably in just two, three or four places) and the entire document updates to the new fonts.