We intentionally chose for the expenses in a group to be visible to all members of that group – we’ve found that it makes it easier to fix errors when someone makes a mistake (e.g. someone is accidentally included on or excluded from a bill).

However, you can also add expenses that do not belong to any group, and those expenses will only be visible to the people involved. If you are in a group with many transactions that do not involve you, you may find it useful to get rid of the group entirely, and just add expenses directly with the people involved.