There is a concept of blocks in mycomarkup, and some built-in blocks: table, img. It would be super useful to have some way to define custom blocks with this syntax, like: spoiler {hidden content}, html {custom html code}, js {some code that can be executed in place}.

Main problem would be - how to define this blocks? Probably, the easiest way is to define some module inside mycomarkup library with those blocks and to allow user to choose which version of mycomarkup to use with mycorrhiza