More loosely relates to these issues: MC-144009 MC-145821 MC-164001 MC-165403
The bug
None of the button textures used for the resource pack or data pack screen will render translucent pixels as translucent if provided a texture containing them.
How to reproduce
Download and apply the attached resource pack
Re-enter the resource pack screen
Expected results
Translucent triangles.
Actual results
Opaque triangles.
Linked issues
relates to
Attachments
Comments

Can confirm. Affects 1.20.5 pre-release 1.