Adding Freedesktop compliant *.desktop entries
OpenBSD has some useful base applications that do not have menu entries. I have provided ~/.local/share/applications/*.desktop entries for xterm and xcalc along with an expanded ~/.Xdefaults. A classic Ti80 calculator look for xcalc is included. You can look at the examples and reference this Arch Linux wiki in order to generate additional *.desktop entries:
Desktop Entries - ArchWiki
If you want to modify the ~/.Xdefaults file, this is a good guide:
https://wiki.archlinux.org/title/X_resources
In newer linux distributions Xresources provides the same configuration but requires xrdb to implement any changes. OpenBSD still uses ~/.Xdefaults which is read on each login.
The Arch wiki also details how to avoid duplicate desktop entries in case there are duplicates in /usr/local/share/applications and ~/.local/share/applications. Just append
to the entry you want to hide.