I'd also like to do this in the Rich Text Editor... I do not want to use Markdown and anything in MD for indents is a workaround.
I really don't understand why this is such a problem with these apps. I understand that MD doesn't support indentation, but these are reasons why people want to use Rich Text.
Why after years does of people asking for this, is it not a thing? Truely I'd like to understand why something as simple as indentation is such a hard problem to solve.