What I’m trying to do
Be able to make use of the full width of my screen by having lists in multiple columns that i can edit using markdown
This is how to use Markdown inside HTML blocks until i read to the end of the thread and saw that that workaround no longer works.
Is there any other way that I can manage markdown lists but have them be rendered in multiple columns?
This is not possible. Markdown cannot be used inside HTML. Only HTML can be used inside HTML. As the thread you linked inferred, it was an unsupported happenstance (a bug) that that it was possible for the time it was. Even if you could find some way to do this, I wouldn’t rely on it.
Why not create Markdown tables and adjust width with CSS snippets?
because markdown tables don’t support multiline cells, which makes markdown lists of any length completely unusable.
(transclusion is a workaround for some use cases i have, but not for checklists, which is my main use case.)
(marking this solved because i asked the original question too narrowly and that question was correctly answered. will re-ask more broadly in a different post for better future searchability.)