I already start by saying that, I know that mending is an enchantment treasure, and I know that you have to put precious blocks in a 3x3 below him, but the problem is not this: I make you understand the problem through a video
https://youtu.be/pot6DK2rL4M
Put simply, mending is not ... let's say "Shown" even completing all the requirements (precious blocks and day light). But it appears if you use the mouse wheel

Mod version: EnchantingPlus-1.12.2-5.0.179

And besides, if I try to apply "Mending" then it disappears funny

EDIT: Ok nothing, it disappeared because it was night, but the mending bug is not visible remains