Clicking and dragging between markers, if the appropriate Snapping option is enabled, should make it simple to select this region. Range markers (markers with an assigned duration) will select the duration when double-clicked. I have seen a few requests for a simpler "select between this and that marker" tool, and have added this feature request to our database.
the snapping worked well for me the first few days, and has since seemed to malfunction. Do you know where I can go to make sure it is turned on? thank you.