Description:

If an item of the same id as one of the items displayed on the creative inventory tabs (e.g. an Iron Ingot) is given a cooldown using the use_cooldown item component, the white item cooldown overlay will display over the corresponding tab icon when it is used.

How to reproduce:

1. In creative mode, give yourself one of the items displayed on the creative inventory tabs (bricks, cyan wool, grass block, etc.) with the use_cooldown component and consumable components added. One example command I used:

   /give @s minecraft:grass_block[minecraft:consumable={seconds:1},minecraft:use_cooldown={seconds:8}]

2. Consume the item.
3. Once the cooldown overlay appears on the item in your hotbar, open the creative inventory.

The cooldown overlay will then appear on the creative tab displaying the corresponding item.