I use this CustomBuildAction
but after debugging my app (in rare cases) B4A delete all folders from res directory except drawable, layout and xml.
So my folders drawable-xxxhdpi, drawable-xxhdpi, drawable-xhdpi, etc, are deleted.
B4X:
#CustomBuildAction: 1, c:\windows\system32\attrib.exe, +r res\*.* /s
#CustomBuildAction: 4, c:\windows\system32\attrib.exe, -r res\*.* /s
So my folders drawable-xxxhdpi, drawable-xxhdpi, drawable-xhdpi, etc, are deleted.