Currently, if you need to filter out selected objects from a list based on an association (*-* or 1-*), you need to either use a DS microflow to filter out already-selected items (if you are not committing changes/using cache, this is a must), or use XPath (requires committing changes when selected objects change). This is a very laborious/repetitive task, and it still causes issues, e.g. when your list-entity has over 200k records; if that is the case, the only way to go forward is to commit each list-change, which is a shame.
I propose adding a check-box feature to datagrid and datagrid 2, where if checked, any selected (either cache or db, but cache takes precedence) items are automatically filtered out.
Please vote for this idea if you like it !