What problem does this address?

When using the block 'move to' option, the keyboard controls aren't very clear. The idea is that:

• up/down arrow keys to move before/after
• left/right arrow keys to move in and out of nested blocks (that are below the indicator).

The feature was mostly developed for screen reader users, but there's no reason it can't work equally well for everyone.

What is your proposed solution?

Show an on-screen guide when Move to is active.