Okay, my request is now solved.
The CodeMap extension, is basically the extension I’m looking for.
I followed their guide on https://github.com/oleg-shilo/codemap.vscode/wiki/Adding-custom-mappers
I created a custom dedicated mapper “mapper_X.js” saved it to an arbitrary location, and in my vscode user-settings I pasted "codemap.X": "mylocation\\mapper_X.js", (as described in the github guide). I then opened up a new file, saved it as untitled.X and typed some syntax (the example code in my question), now I could see my custom outline.
As could be seen in the result-link below I have (deliberately) not defined my mapper to consider any other cases yet. My mapper is still in its infancy state. Just thought I’d share my findings before I forget I posted this question…
