Gotta let this go, so I can do some other things tonight so will share what i currently have...
What I did was (and its way easier I think than using Gem) was write a (bash) shell script which reads a (linux-only I'm afraid) right-clicked file, i.e. a *.pd file, which you then send-to the script and it outputs a (plant)uml diagram of the objects within the patch.
Actually it outputs 3 flowcharts: native objects, subpatches, and abstractions.
I (currently) am only able to identify "natives" as what i scraped together from the Help folder so it's really quite bare and does not include all the aliases. (If you wanna have a go at amending that it is at: (when unzipped) "/root/pd-externals/pd2plantuml/res/objectlist.txt".)
On the other hand, it could be amended relatively easily to also include all externals and filter similiarly for them.
So if you unzip the file below in your ~/pd-externals folder and then point a right-click event to: pd2plantuml.sh you should then able to output the mindmap which opens in your "defaultbrowser".
Couple of caveats: plantuml has a lot of reserved characters and the current version does not account for all but one of them, "~", so it may balk on certain file(names) and complex files do take a moment or two to generate.
Good will and love thru us all.
Feedback welcome as this was a pretty fun and relatively stressless endeavor.