I have heard from users that when they are in the To Approve inbox or To Enter Inbox they are unsure what clients have transactions to deal with so filtering the boxes is not as useful. With a Collapse all button they would be able to view each client without having to scroll through everything. Also the collapse buttons already exist on the clients so having a button to collapse all should not be difficult to add.
YES! This is very important. This should be a priority. Many of us work with more than one group, so there is an excessive amount to scroll through.