Use a file manager to place your .ttf/.otf files directly into your main Kustom/fonts/ folder.
Go to KWGT Settings → App Settings and re-select/re-assign your main Kustom folder. This will force Android to update storage access permissions for Kustom.
Force stop KWGT and clear its cache.
Open KWGT, go to your text item, and instead of scrolling, use the Search function at the top to type the exact name of your font.
Make sure that the Source filter in the font selection menu is set to “All”, so it searches both system and your custom local fonts.