Dmenu is hard to describe. It's often called a 'dynamic menu'; at a technical level it's a pop up text entry widget with autocompletion (with what it autocompletes taken from standard input) that prints your entered (or autocompleted) text to standard output. I've been using dmenu for quite a while and as part of that I've built an elaborate setup around it. One of the things my dmenu does is run commands, and part of my setup is that I invoke commands with a custom $PATH with a collection of directories that are only used for dmenu.

(This element of my setup has been there from the beginning.)

What I put in these custom $PATH directories is a collection of little programs, often with extremely short names. Effectively, these create abbreviations for commonly used things. For example, one such program is called 'g'; it uses Firefox remote control to open a Firefox window that's doing a web search on whatever command line arguments it was invoked with. These command line arguments come from whatever else I typed in dmenu, so I can type 'g dmenu arch wiki' and have a Firefox window open with the results you'd expect. Another little program is called 'pd', and uses Firefox remote control to open a window on the Python website's page for a given package in the standard library (eg 'pd time').

(A significant number of these small programs use Firefox remote control to open Firefox windows on various URLs, because it turns out that visiting various sorts of URLs is something I do a lot.)

My various custom $PATH directories are separated by both their purpose and their visibility in dmenu's initial list of completions (having dmenu completions that aren't initially visible is a personal feature I added that turned out to be quite useful). Because these directories aren't in my normal $PATH, I can load them up with very short names that might cause problems in normal shell usage (or clash with real commands that are only a few letters long), I can use names that I wouldn't want to be commands normally, and I can 'reframe' regular commands to be run with special arguments or special argument handling that makes them more useful in the context of dmenu.

(I can also create short aliases for commands, if I want to.)

One of the things I don't do as often as I should is go through all of these special dmenu $PATH directories to weed out things I'm not using any more (and things that I thought I'd use when I created them but I was totally wrong). In practice, a lot of my clever ideas for short things have turned out to not get used.

Special directories with custom scripts in them isn't the only way to implement this sort of thing. Dmenu needs a wrapper script to do things with its output, so you could put the intelligence into the wrapper script (and my dmenu wrapper has a certain amount of that). However, I've found it easier to modify this sort of abbreviation by adding, removing, or changing a little script than by always editing my dmenu wrapper script.