Here's the wiki page that lists everything that you can put into a table_dynamic:
http://hlkitwiki.wolflair.com/index....Element_(Data)
You're going to use either the secondary or existence option for this.
In this scenario:
The user starts adding spellcasting this way, and adds a few spells, then changes their mind and deletes the option that gave them spellcasting, and then changes their mind a second time, and re-adds spellcasting (they might re-add it using a different option that grants spellcasting).
If you want the same spells they selected earlier to re-appear, use a secondary expression for this. In order for this to happen, the spells are actually still present, but non-live while they can't cast spells.
If you want the spells to have been removed as soon as they turned off spellcasting, use an existence expression. This would be more appropriate if you can get to spellcasting multiple ways, and each one has different lists, and you think it's reasonable that a user might change their mind during character creation as to which way they want to add spellcasting to their character.