In reply to CW.

I talked about the vertical issue with Twenty Twenty-One. Then, I solved it with Eksell's custom No Vertical Margin style. I just removed the margins between different sections. I could've used it between the first and second headings there. However, I could not with Twenty Twenty-One.

Agreed on margin controls for end-users not being the ideal solution for this. The primary solution is for themes to offer pre-built block patterns. The margin controls should be there for advanced usage, but smart design choices should be the default, and that comes down to the theme.

A block variation/style for a "subtitle" would be a good addition too.