[ShadowWalker]

I'm going to use pathfinder as an example.

Add a level of cleric. Then add your domains and spells.
If you were to then delete the cleric level and re-add it back then the user created picks on the cleric tab for domain and spells are gone.

How exactly do you do this?

I have a situation where the option to choose something may go away based on other choices made and so if the user changes their mind I need to be able to clear choices made.