Make Inkscape's font dropdown show only fonts you have active in Font Book — instead of every .otf/.ttf on your Mac including Apple's 300+ language and decorative fonts (Devanagari MT, Kohinoor Devanagari, Kannada MN, PingFang, Osaka, Chalkboard, etc.) and its ~80 dot-prefixed hidden system fonts.
Inkscape on macOS uses Fontconfig, not the native CoreText / Font Book stack. Fontconfig scans font directories directly and doesn't know about Font Book's activation state, so every font on disk shows up in Inkscape's dropdown regardless of whether Font Book has it enabled. On a stock macOS install that means hundreds of fonts, most of which you don't use.
Compounding the problem: Inkscape.app's bundled Fontconfig has been hand-edited by its maintainer to strip standard user-include paths. So even if you write a ~/.config/fontconfig/fonts.conf, Inkscape.app never reads it. This is why "just add a fontconfig" doesn't work.