Here is a short explanation on how to use showcase:
Usage
Adding a showcase
Start sneaking!
Right-click a half-step block with the item in your hand you want to showcase
An assistant will ask you which type of Showcase you want to add. Type the text before the colon )
Depending on the type you chose, the assistant will ask some extra questions, follow the assistant to finish showcase creation.
Removing a showcase
Sneak
Right-click on a showcase. If this was a finite showcase or an exchange showcase, you will get your items back.
To buy, right click on the showcase.....
Usage
Adding a showcase
Start sneaking!
Right-click a half-step block with the item in your hand you want to showcase
An assistant will ask you which type of Showcase you want to add. Type the text before the colon )
Depending on the type you chose, the assistant will ask some extra questions, follow the assistant to finish showcase creation.
Removing a showcase
Sneak
Right-click on a showcase. If this was a finite showcase or an exchange showcase, you will get your items back.
To buy, right click on the showcase.....