What does select filter do?

Enable this option. Select an item and go the trash tab. Now in the bottom right, click the "Custom" button. Now, if you go back to the edit tab, you can only select items that are of that first item's type. If you try to select another item it will just not select. This still works for swiping.

To be able to select any item again go back to the trash tab and click the "None" button.