It is probably obvious and I'm blind, but I don't see a trivial way to define from the GUI, a user who can only manage some VM (start, stop. reboot, open console), and nothing else.
Where is the trick?
In my request I ask for a "trivial" way to do something that, in my mind (may be I am wrong), is relatively simple.
From the docs (included the reported link), seems simpler to do this administrative tasks from command line that form the GUI.
A Proxmox administrator usually isn't a standard user, but I think that he also, expects that for using a GUI they don't need to study the pve2-api-doc (good activity, but little overkilling for the needs). IMHO this type of common task have to be solved selecting the available resources in a combo box/list o similar.
Very appreciated if anyone that have already studied the pve2-api can write an example of the commands needed to obtain was I am interested that (I think), can be useful to other people and added as example to the wiki.