As I did with Keyboard Maestro 8, I will endeavour to post some tips about using the new features in Keyboard Maestro 9.
The first one is that you can now create a second (or more) editor windows by using the File ➤ New Editor Window menu.
The windows have independent state, so you can edit one macro will viewing another macro, making it easy to drag-copy actions from one macro to another, and they remember all their details on relaunch as you would expect.
Note that there is a performance penalty in this, since Keyboard Maestro has to update both windows, and particularly if you are editing the same large macro in both editor windows you will see some lag as Keyboard Maestro has to re-generate the other window’s macro for each change. But in most situations this should not be too much of an impact.