@warner You could, but the timeline will open as well. I've set up a Shortcut for making quick posts. When triggered (via keyboard shortcut, dock, or "Hey Siri, new post"), I'm presented with this:

A text field with the title New Post – What's the text? – and two buttons, Cancel and Done.

I write my post, hit Done, and it's on its way. (Old iOS screenshot, but it runs on macOS as well.) @gr36 published two Shortcuts you can use as a starting point in his post How To Publish To Micro.blog With iOS Shortcuts.