Using third-party app for editing

You can edit your artwork with third-party apps via settled paint layer in RGBA mode. You can use 2D stamp brushes, selection, liquify or warp tools that are available in those apps. You can also use those apps to save extra layers as RGBA image files. Known apps to support this are Paint .NET 5.0.8+ and Affinity Photo 2. FYI, other apps that support such data exchange via RGBA bitmaps include Clip Studio Paint and Krita, but unfortunately, they would have the image shifted after copy-n-paste. Adobe Photoshop doesn't support general RGBA bitmap copy-n-paste.

Please see video here: