I just tried to make the multiblock structure for the improved coke oven realizing afterwards that it's disabled.

I noticed that there's no entry in the engineer's manual for it, but I still tried to make it.

A tooltip on the reinforced coke brick saying that the improved coke oven is disabled would've been very useful, so I'm just suggesting it as a possible improvement.

I attached an image of the multiblock structure in case I did it wrong and it's not disabled.
(3x2x3 reinforced coke brick, 3x1x3 steel sheetmetal, 1 hopper)

I believe you did it incorrectly, as the improved blast furnace is assembled using a 3×3 cube of reinforced coke brick, without any steel sheetmetal.

Yes, that's the way to make an improved blast furnace, but I was trying to make an improved coke oven, to create creosote oil and coal coke.

This one right here:

Thank you for report!
Yes, I could add tooltip and probably note in quest book.