When I write a YAML pipeline, I can obtain that start values are chosen from a collection of static values specified by me (provided they are at least four):

Those values become available from a combo box at runtime:

However, when I am composing new tasks using the wizards provided, there are combos that are filled with values captured on the fly, e.g. from my artifacts:

I assume there are some API's that the wizard invokes at runtime in order to fill the combo with relevant current values.

In particular, I am interested in API's that interrogate Azure Artifacts.

Is there a catalogue of such calls?

I found some food for thought in this and this other SO question, but I am still searching.

I have found the code of the task wizard that interests me, but I haven't found the API calls yet.