How do I change transactions from deposits to expenses

Delete it.

QBs gets funny about those things.  It won't let you just go change the associated Acct when it first went in as a Deposit.  It will let you pick another Bank Acct, but not any other kind of Acct.  So just Delete it and start the process over.

Agree with Pete. Money coming in vs. money going out are two different functions so would need to reverse the first and input new transaction as what it really is. Could get messy allowing corrections to standard entries that are setup to help guide you in the right direction. First always determine if money came in or out to choose.