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. 