[Request] Customization of left item

Ability to change Material, Lore, CustomModelData, ench(etc) of the left item would be good.

Also actions([Shift ][Ctrl ]<left/right/middle>) such as setting emails(authme)(Another anvil gui opened to set email maybe), running a command(console/player) and stuff would be good but i think it will kill the user experience/easy to understand login screen.