wrote:

As this illustration shows I think you will not be able to pull the lock down and out until you have pulled the side away.
https://s3files.core77.com/blog/imag...ocknuts-02.jpg

because of the slot in the cam, you can pull it out when pointing the
right way (after all, you do insert it after the dowel in the first
place) but as Richard points out, the dowel will still be in place, if
you can't spring the sides apart, judicious use of a multitool to cut
through it will release the shelf, but then it'll need supporting on a
batten or similar in its lower position.