Work in progress - movement is in-built account that is used by Billable time module. It is not possible to debit/credit this account, transactions in this account are automatically generated based on billable time entries.
Are you using Billable time tab? If not, disable it, otherwise you will have in your Chart of accounts accounts which you don’t need.
Then just create your own custom accounts under Chart of accounts which you can debit/credit without restrictions.