Cool. I must be doing something wrong thenYou can do this right now with Axe-Edit as this is functionality built into MacOS and iPadOS (assuming your Mac and iPad meet the requirements). Axe-Edit does not need to do anything special to support SideCar - just drag the Axe-Edit window to the iPad display when you have connected the iPad through SideCar.
Note that the default Axe-Edit window size is too large for the typical iPad display so just go ahead and resize that window - or click the + icon (upper-right of Axe-Edit) and the window will adjust to fit within the display size.
If you're using older Mac devices which don't support SideCar, try the Display Duet app. Turns the editor into a touch screen app. Works great and pretty fast.