Once you have created combined rows in Float these can be quickly removed if required, using the View options dropdown on the main cash flow page and then clicking on Personalise accounts.

The combined row will be easily identified from the list of accounts similar to the example here:

Clicking on the 'Bin' symbol at the end of the row will remove the combined row and add the individual accounts back into the table.

Please note: Removing a combined row will also permanently remove any budgets associated with it.