Right-click and select EDIT. To move along the timeline place the cursor above the blue line, click and drag to the place you want to marker/cut and use the scissors ( to the left)
To cut the selection, place another marker/cut and select the portion you want to delete and hit the Delete key.
You can also drag both ends of the timeline like you would do when editing on the iPhone or iMovie
Click on the 3 dots to compress the file like before