For a complete answer on all of the ways to delete measures in Notion 6, you will want to refer to page 6.8 of the User Guide. In short, you can press "Escape" on your computer keyboard to arm your mouse pointer with the select tool, click and drag to select the desired notation, and press "Delete." If you choose Edit>Delete from the menu bar, the highlighted notation, along with the bar line/s will be deleted.