The bug
The green and white progress bar displayed in the toasts which appear when starting the game cannot be retextured at all.
This is inconsistent with some other progress bars in the game, such as the bundle fullness bar (MC-275778), boss bars, the experience bar, horse jump bars, villager experience bars, and more.
How to fix
Introduce actual texture files for this bar.
Linked issues
relates to 29
MC-278413
Chat background cannot be retextured
Open
MC-268805
panorama_overlay.png no longer works
Resolved
MC-268927
The dark background in inventory screens cannot be changed via resource packs
Resolved
MC-269079
Death screen background cannot be retextured
Resolved
MC-269364
Sign editing screen can no longer be retextured
Resolved
24 more links
Can confirm.