Heading Block: Allow quickly adding specific heading levels

[shaunandrews]

Right now, to add an h4 to my document I need to add a Heading block and then use the block's toolbar to select the h4 level from the menu.

I often add the Heading block from the / inserter:

What I'd love to do, is to type /h4 and have the Heading block added with its level set to h4. I think we could do this by creating hidden variations of the Heading block that would only appear when searching.

[diegohaz]

That would be really good!

I used to type /head + Enter as well. But since I always had to change the heading level manually later I trained myself to use #### + Enter (which would create a heading level 4).

I would like to keep typing /head though as I feel more confident doing so (sometimes I type the wrong number of #).

I also think the /head popup could suggest different levels of heading based on the current document structure. That is, if the last heading is level 2, we can show heading level 1, 2 and 3. I think we can safely omit 4, 5 and 6 in this case.

[talldan]

Duplicate of #7438, fixed by #26597