Is the thumb latch reversible?

You cannot adjust the thumb lever for our 82-086, unfortunately. It is fixed in the bottom position permanently. Since you need a thumb lever in the centered position, then I would recommend the 82-030 handle set, instead. If you need a key lock then you can use the 82-310.

You'll note that the exterior handle has a protrusion in the middle of it. That protrusion has three knock-out holes that you can punch in order to install an 82-310 key lock.