Converting Accounts to be Open Item Managed

We're attempting to convert some of our GL accounts to be open item managed to assist our accountant tracking new store construction. We've made the balances zero, but are still encountering errors when we attempt to save after adding the Open Item Managed flags to the appropriate GL account. We do not want to create additional GL accounts, and add to the clutter of our Chart of Accounts. The error is FH190 and references some ECC notes and procedures which aren't really applicable to the S4HC.

Does anyone have any experience converting GL accounts to Open Item Managed in S4HC or know what the desired procedure is to get the existing account converted?