Both Keyboard Maestro and BetterTouchTool both have the ability to create a floating menu that could be called up at a gesture or click and contain whatever items you want. You could also make a single command always appearing as a floating button whenever Scrivener is focussed.
If you don’t have either but want to look into it, I’d focus on BTT as more mouse-oriented; here’s a page with examples of various floating menus and widgets.
Yeah, on Windows I created a floating palette using AutoHotKey to automate my frequently used commands (FUCs). 
However, in the end I realized that I am one of @Silverdragon’s YMKS people — self-knowledge is important, and this became a learning experience for me — so eventually I migrated this palette to be invoked via one shortcut, which gives me instant access to all of my FUCs.
Best,
Jim
Although, as noted in the other thread, you’re breaking your own source material by doing that, if you’re using Scrivener to produce Markdown! So maybe one less command to use frequently. 
How do you get scrivener to produce markdown?
so far when I have tried:
Paragraphs don’t have a blank line between them.
words that i make bold are not *bold* in the output.
styles in scrivener that are marked “Header 1” don’t come across with hashmark
If you’re trying to convert from rich text to Markdown as it sounds like you are, then you need to enable the Convert rich text to MultiMarkdown checkbox, in the General options tab of the compiler overview screen. This will of course only show up when one of the Markdown-based output options are selected from the Compile For dropdown.
But really that’s more of a transitional tool, or one you might use if you really only want one of the formats provided by MD without the whole package. That checkbox aside, the program is designed to be used as a Markdown editing platform, where your source text already has properly spaced paragraphs, you aren’t using font variants to signal intent, and most likely your heading structure is coming from the binder titles and the organic structure of the outline, rather than text typed into the editor (but if not, you can still use the Styles compile format pane to insert hashes before the text as a prefix). See Chapter 21 in the user manual, or this thread.