A solid non-conductive block.

So with redstone, when traveling up 1-block inclines, you can place a solid block above that to cut off the redstone signal. With transparent blocks, the redstone signal is not cut off, and can go up that one block step.

This is a very useful feature, but the problem is that all solid blocks conduct redstone signal, while all transparent blocks do not.

I think it would be useful to have a single solid block (that you can still place redstone on top of), that does not conduct a redstone signal into it, but does still cut off 1-block inclines.

I would suggest a current, completely unused block, such as the nether wart block.

It would just be a small, niche feature, but it could help compact a couple redstone circuits, and would be an interesting mechanic to play around with.