Following https://bugs.kde.org/show_bug.cgi?id=435372 It is extremely hard to know that that "variables" can change rendering features like font family and size due to the place it is put. The UI/UX can be enhanced in a way that the variables are (for example) a listbox like shortcuts dialog. Plus adding it to the documentation. And perhaps having some help in the color schemas window for people to know how to change font.
Improvements are welcome, if you have some time, please provide some patch if feasible. https://kate-editor.org/post/2020/2020-07-18-contributing-via-gitlab-merge-requests/