I hacked them off. Later, I would be replacing these original screws with some that were 1 1/2″ long to go through and attach the bottom ledge from behind.
Here you can see the 1 1/2″ screws in black which go through the back block, the spacers and into the bottom ledge. The bottom ledge is one half of the folding lower ledge of the original easel. The knurled brass nut is the original nut to secure the sliding upper bracket bar.