Summary: If a Addon Maker would attempt to create a custom hud_screen for a block or item its impossible to link the UI to a event to be triggered and have the UI opened correspondingly. However if you download a Offhand Slot Resource Pack in MCPEDL the Hud_Screen works properly when holding a item but doesn't trigger when right clicking a item or block because you can't tell the UI to open the Screen.

Steps to Reproduce:
1. Download the Resource Pack on MCPEDL.com called Offhand Resource Pack.
2. Load a World with Resource Pack Enabled.
3. Hold a Item like a Totem in the Offhand the the Totem will be Displayed as a Screen where the Offhand Slot Should be.
4. Download Vanilla Resource Pack.
5. Find UI Folder.
6. Find a Screen then Rename the Screens Title which is the Corresponding Block Name.
7. Rename to your Custom Block or Item Name.
8. Load the Request UI Event in the Vanilla Behavior Pack Documentation.
9. In Manifest.json put experimental_ui in capabilities.
10. Make a Folder Called Experimental_UI and Scripts.
11. Add Client and Server Folders to Scripts Folder.
12. Add the UI Request Event to the Experimental_UI Folder.
13. Add a Menu Folder.
14. Put Hud in There or HTML UI.

Note: In the Java Script System there is a Component Called Load UI and It is Possible to Get a Item with approximately 100 lines of Java Script to load a UI but not a block or item with a regular (name)screen.json

Link to Other Bug Report: MCPE-138133

Observed Result: The Hud_Screen Won't Link or CustomAnvil_Screen won't link properly to the Block or Item this bug is also dependent on the bug linked above.

Expected Result: The Hud_Screen or CustomAnvil_Screen Should link to the block or item.