Working on some bigger placeholders can get tedious very fast, especially once you get past 2 layers of nesting.
It would be cool if placeholders were to collapse into some compact form of themselves.

Also another thing that would help is allowing line breaks. Not sure why it was implemented so that you cant, but it would be cool if you could style your actions with line breaks and tab characters, that might get removed or ignored when actually reading the file.

The one-line thing is like that because otherwise people would forget about spaces at the previous line's end, which would break some placeholders and it's not always possible to know which spaces are supposed to be there and which aren't, so multi-line support will probably not happen in the near future.