Where should I put my contracts money when I don’t have any positions open?

I have 3 accounts I trade from. An IRA, and 2 margin accounts. One for stocks and one for options. I split up the accounts so they can each have their own bankroll.

I only open positions when I’m not uncertain. Sometimes I go a while without busting a move. I usually take the options bankroll and throw it into apple or VOO until I find a new trade.

Should I be doing something else entirely? What stock/fund do you guys use a parking spot?