Make it possible if this is a vanilla ender-chast (without the main menu), then you can add your own items and when you click on an item, then some command is executed (The command indicated by the user)

Hello, can you precise your idea @EneRGO22? I do not understand what do you want me to add to the plugin.
Because this plugin is not a custom GUI plugin.. adding custom items with configurable commands does not fit in?

In the main menu? Because that does not make sense to add custom items in an enderchest.. they are used by players to store their personal stuff. In that case I don't know how to help you.

Look, I want to use the vanilla ender honest and by default so that all slots are open, but I want to cover everything with glass panels except for the first 3 rows in the ender, and make an item from below, for example, it will be a stone, and for the player to click on it and perform some then the command, in my case, is adding a permission to the player and withdrawing money

By default, the player should have such an ender chest

He clicks on a flower and one row is added to him

Well, when the player clicked on the flower, he checked if the player had a certain amount of coins, if not, he wrote a message that there were not enough coins

Здравствуйте, вы можете уточнить свою идею @ EneRGO22 ? Я не понимаю, что вы хотите, чтобы я добавил в плагин.
Поскольку этот подключаемый модуль не является настраиваемым подключаемым модулем графического интерфейса .. Добавление настраиваемых элементов с настраиваемыми командами не подходит?

I want to be able to add my items to the menu

Oh ok that's an awesome idea! A kind of way to level up enderchests, I appreciate it a lot. But Its not planned for a near future..