For spells I would put it with the range in the string field.
For spells slots you just need to edit char_abilities xml.
For npc intelligence you might need to use notes tab as I'm not sure it's going to add any automation.
For skills a change to the code or an extension will be required. I might change the ruleset code. There are some OSE optional rules that use custom dice rollers.
For levels the code goes to max 14 but you can level manually if needed.