Good point. Agree that this would be a significant and welcome enhancement.

And I don’t care what DT’s editor is missing
As you’ve made abundantly clear.

We’re going in circles here
My point is to simply describe my frustrations with the current state of MD support in the editor, to propose specific enhancements, and to add my voice to others’ in general support of enhancements to the editor.

Should the DT people prioritize MD over PDF or image editing? Why?
That, of course, is up to the DEVON team. And they clearly do listen to their user base, who are expressing their opinions here, indeed, as you have above with your observation that enhanced search would be useful.

Or should DT users employ dedicated tools fulfilling their requirements?
“should DT users employ dedicated tools…” is not exactly the question here: some users are in effect forced to employ additional apps to achieve their desired results. But, other than this, of course, it is up to individual users to make do without, or to employ additional of apps at additional cost and burdens (maintenance, compatibility,…) and inconveniences ranging from trivial to significant, to achieve their goals. For some, enhancements to the built-in editor are more supportive of their goals. as they have described.
Of course, all are free to agree or disagree, with any opinion, observation, or proposal. But to express surprise that such opinions exist, and to cast the question as a simple take-it-or-leave-it choice, is…surprising.