I never add a new custom device with the new in-App,
I created a new device handler from the code and publish but don’t seems to find a way to add on the new app (and the classic app don’t have support any more so can’t do from there neither)
Click + (plus) in the upper right of the screen, choose Device, choose tHe by brand section then select scan nearby at the bottom of the screen or z-wave from the list for z-wave devices but scan nearby should also work