The bug
If "Pick block" is set to a key, it doesn't work in the Creative inventory.
To reproduce
Rebind "pick block" to a key, for example Right Alt or V.
Put an item into the hotbar.
Open the search tab on the Creative inventory
Hover over the item in the hotbar and press the pick block key.
→ ❌ In case of "V", that letter gets entered into the search bar (might be intended), in case of right Alt, nothing happens (probably not intended).
Related issues
is duplicated by
Comments

@unknown, that sounds like a separate issue. If we don't have one already, please create a new ticket for that.

Still an issue, as of 1.16.4, on MacOS version.
Validated the inconsistency with a USB mouse (works as intended when bound to scroll wheel) and when re-mapped to other keys or even the Macbook Pro trackpad (can'd drag to duplicate).

This is still true in 1.19.0 Java on Windows. It works if I reset the "pick block" keybind, but not when I have "pick block" bound to a different key.
Specifically in the creative inventory SEARCH tab. The other tabs without text input work.

Can confirm in 1.19.3.

Confirming this bug is ongoing in 1.21.1, and is a major accessibility issue.

This issue still occurs in Minecraft snapshot 24w44a despite refactors to the pick item functionality.
Can confirm. Another smaller, but related bug, is when you press Shift+3, for hashtag, it instead puts the item you may be hovering over into your third slot instead of typing a hashtag into the search bar.