To share some orthogonal ideas: how I work is to find a way to have the best of both worlds, rather than a really cut-down version of one world (which I think is the best you’re ever going to get from macros, text expansion tools and such).
- A basic introduction to the idea, as well as its limitations and when I stop using it, or gradually stop using it.
- A more detailed post on setup ideas.
- And since you mention preferring Obsidian’s typing tools, here is a setup how-to specifically designed for that pairing.
This way of working dodges multiple problems, most of which all stem from how Scrivener’s weakest point is its text editor. Anything starting from a “word processing” baseline is in my experience going to be pretty weak. At least I’ve never seen anything in the LibreOffice, “Google Docs”, Word, or even WordPerfect spectrum that remotely approaches the utility of a text editor like Sublime Text, VS Code or Vim—and with those you can add Markdown typing aids on top of them.[1]
And that’s what it really boils down to. Could I put Markdown typing aids on top of Scrivener’s editor? Sure… but why? It’s still a word processor style text editor that is (excluding all the fluff about rich text) realistically about as capable as the box I’m typing into, in this browser, while responding to you. Ctrl+End, Ctrl+LeftArrow, Ctrl+C, Ctrl+V… not much. Or, I want to avoid having a really cut down version of one thing (basic macros instead of a full Markdown writing suite), but if you put basic macros on top of a really basic text editor—isn’t that the worst of both worlds?[2] 
But, to answer your actual question, yes something like is probably a good start:
I bet it wouldn’t be hard to modify some of those to allow for a hybrid approach of it being more for modifying existing text. For example, selecting a word or phrase and pressing Alt+B to wrap it in asterisks is way more useful to me. If I were designing this, that is 100% more the route I would take. I’ve never quite understood memorising keyboard shortcuts to insert characters that take just as much effort to type in directly. Isn’t that a major selling point of writing with Markdown, that you can just type it all out easily?
On the other hand though, something that takes a URL from the clipboard and produces, [Previously selected text](clipboard)? Absolutely, why not. That’s demonstrably easier, as is even **previously selected text** (though, the latter is again much easier in a proper text editor rather than thrashing about in something that bumbles through text like a word processor).
Curiously, I find Obsidian’s editor to be about equally deficient in these regards. I suppose for that matter a lot of custom built Markdown editors may have that same flaw, and maybe that’s why I’ve generally always preferred coding editors with Markdown plugins. ↩︎
I mean no offense at all to the macro creators out there! The point is, there is only so much you can do without a full plugin SDK. ↩︎