Krita

• You can run Python from Tools/Scripts/Scripter
• To make a Python plugin, see the Krita docs

Icons

list all icons in Krita

from PyQt5.QtCore import QDirIterator

it = QDirIterator(":", QDirIterator.Subdirectories)
while it.hasNext():
    name = it.next()
    if name.endswith(".svg"):
        print(name)

krita has an icon browser build in the python dev tools

default qt icons are also available, see Qt TODO figure out and add instructions how to add custom icons

other

labeled separator & tooltip & icon are not in any of the default Krita menus, but they can be achieved with UniMenu in Krita.