Ackchyually XDG default applications aren't set via env vars but through the `${XDG_CONFIG_HOME}/mimeapps.list` file manipulated (either via text editor if track desktop files yourself or, better) via `xdg-mime {query|default}` tool. This TUI is a replacement (doesn't wrap it) to this tool for this functionality, with twist that does multiple-defaults category-wise rather one-by-one ("word processor documents" rather odt/doc/docx).
Compared to what slopcalypse has brought, this one (project; vibe coded maybe, certainly not slop) at very least is useful (also is quite short; within a sea of thousand LOC generated in 1s this is refreshing).