Visualize the block about to be moved when in "Move to" mode

[t-hamano]

What problem does this address?

Suggested by this comment

Select Move to from the block toolbar and a blue indicator will appear. This indicator can be manipulated using the arrow keys to know where to move the block.

However, it is not visually clear what block is about to be moved.

What is your proposed solution?

To solve this problem, I think it would be effective to hide the block that is about to be moved, or to give a visual change to the block.

For example, when a block is dragged, a light background is applied to it.