Is there a reason you want to limit this to separable verbs? Because it works the same way for non-separable verbs.
The -ung-Form is used to name the result of an action, sometimes a recurring action (as in Leitung or Forschung.)
rechnen (to calculate) → Rechnung (bill)
leiten (to manage, conduct) → Leitung (management, wire, pipeline)
forschen (to research) → Forschung (research)
Nouns ending in -e instead of -ung are not made from the verb but vice-versa, or they just share the same root.
liegen (to lie, to couch) ←→ Liege (couch)
spitzen (to sharpen) ←→ Spitze (tip)
They often have a totally different meaning.
ahnen (to forebode) → Ahnung (presentiment)
ahnen (to forebode) ←|→ Ahne (ancestor)
rollen (to roll) ←→ Rolle (roll, but also role !)
Another list can be made for people or things who/which do something. Still no separable verb required.
rechnen (to calculate) → Rechner (computer, calculator)
leiten (to manage, conduct) → Leiter (manager, conductor)
forschen (to research) → Forscher, Forscherin (researcher)
And another list of nouns prefixed with Ge- denote a tool used to do the action or an alternative result when the -ung-form means something different or is nonexistant for non-obvious reasons.
fahren (to drive) → Gefährt (vehicle)
fühlen (to feel) → Gefühl (feeling) (Fühlung means contact)
backen (to bake) → Gebäck (pastry) (
Backung is nonexistant)
züchten (to breed) → Gezücht (brood) (Züchtung means the action of breeding, today it's used for brood, too)