Since release of another plugin, the Upkeeper, I gained some insight into how I could manage resources in plugin. One option is to provide pre-defined packs using the Upkeeper, or.. integrate a hook, or shade for it.
Also, in a few days, I will add the custom items option (save, load, give, add commands, and effects), and prepare for another phase - which is resourcepacks. As we all know, they are popular, and for a reason.
My experience with them is quite great, and so it should not be an issue.

And, of course, if you are looking for perfect all-in-one custom items solution, you can always reach for ItemsAdder. My experience is only great as for 3 years of actively using it.
I will implement some of it's features, but quite lightweight way, and maybe even add support for ItemsAdder itself.

Let's talk about the tweaks and fixes!

• When you are scrolling hotbar, or.. clicking blocks in inventory, there is a sound played. It is set to block's sound, and so each block you click, or scroll thru, will play a sound, making it way more immersive.
• Several bugs were fixed (and we are finally getting to the point, where bugs are not much of a thing.), including custom GUIs interaction.
• Apart from this, I corrected some translations internally. Actually, I will add messages.yml in next update, so you can customize more and more!

Let me know your ideas, or thoughts - they are very important too!