It’s completely ridiculous that the answer here is “markdown doesn’t do tabs!”
It most certainly does. They’re whitespace, and markdown processors aren’t supposed to screw with them. That’s because Markdown is meant to be read in plain text as much as rich text.
This is an utterly lame deficiency in any kind of note editor, and I’ve just cancelled my commercial license renewal over it and this dumb reply. The ivory tower syndrome with prescriptive workflow in this editor has gotten out of hand.
At the end of the day, Obsidian is a text editor. It does other stuff too, but it needs to be an excellent plaintext editor. Of course you need to allow tabs to be inserted. JFC.