Describe the solution you'd like
An on screen indicator (perhaps near the crosshair) to indicate if vein mining is toggled on (and perhaps one for the mode as-well?).

Why is this feature needed
This is useful for modpacks that use alternative renderers or otherwise obscure the vein mining outlines. This isn't a perfect solution, but its QOL that I think would be expected when most players first learn to use the new system. Typically iconography is preferred, especially for features that could damage things if misused.

Describe alternatives you've considered
The alternative would be to actively support sodium and optifine, which can really suck to do.

Additional context
Example of what I'm thinking:
When vein mining is toggled on: