Step 1
Add a bill task for the property
Step 2
Create a bill titled Wallet Float Amount - DO NOT PAY and create a payment from the owner to the agency.
Due Date should be several years in advance as we don't want to every pay this bill. ie 01/01/2099
Tax Category - select other income, this bill will never be paid so is irrelevant
Step 3
Click Schedule.
The wallet will now show the required amount and hold those funds back in the property wallet.
Once the bill you need to hold the funds for is paid, you can then remove this Dummy Bill so all future funds are paid out to the owner.