This bug occurs on the Nintendo Switch edition, on any world, regardless of gamemode. If the player uses touch controls to navigate the creative inventory, then (WITHOUT closing and reopening the inventory) swaps to using the controller to navigate, the tooltip that displays the names of items doesn't appear. The tooltip reappears and resumes acting as normal upon closing and reopening the inventory, as long as the player doesn't use touch controls. This bug affects any UI that involves the player's inventory, such as the UI for furnaces, hoppers, chests, etc.

Steps to reproduce: 

1. Open any Minecraft world in creative mode in version 1.21.2 on the Nintendo Switch. This can be an already existing world or a new world. This does not have to be done in creative mode, but for bug testing purposes it is faster to use creative mode.
2. Open the creative inventory, and hover around various items with the controller. Notice the tooltip appearing as it should.
3. Without closing the inventory, swap to using the touch screen to select various items in the inventory.
4. Once again without closing the inventory, go back to using the controller to hover over various items in the inventory. Notice how the tooltip no longer appears, even if you select a different tab of the inventory or hover over your hotbar.
5. Close the inventory, and repeat step 2. Notice once again that the tooltip is appearing as it should.

Upon using touch controls, the tooltip will not reappear if the player swaps to using the controller until they close and reopen the inventory.

For clarification in the attached video, the moments where my cursor begins to jump around the screen is when I am using the touch screen, and the moments where my cursor is moving smoothly in a line is when I am using the controller.