With Oraxen ghyph you can create custom GUI's and here is an example
customshop:
texture: custom/default/custom/gui_tienda.png
ascent:13
height:256
code:5088
The textures must be maximum 256x256 and normally they will look a bit uneven in the GUI, so you must use the Oraxen shifts that in your case is %oraxen_shift_-8% or %oraxen_shift_-16% and before that you must use the letter &f in the configuration.
How do I get the unicode for the glyph?
As mentioned in the previous section, you need to get the raw unicode for this.
You can see the command and example here​
How do I create an invisible item?
Invisible elements are ideal for making clickable buttons. To create invisible elements, you will need to make an element with a transparent texture. An example here
invisible_item:
displayname:"<white>"
material: PAPER
Pack:
generate_model:true
parent_model:"item/generated"
textures:
- required/particle
To add a custom CustomModelData use after the pack