Is there a way to set a projects' import settings so that for all imported PNG files the "Alpha is transparent" is ticked? Or, failing that, can this be done by writing an Editor script? It can be done by hand for the time being, but it will need to be automated at some point. Cheers.
You can do it in script using an AssetPostprocessor: https://docs.unity3d.com/Documentation/ScriptReference/AssetPostprocessor.OnPreprocessTexture.html
That's great! ... only the texture Importer docs seem to be missing the set alpha = true part. but with enough iterations of spelling "transparent" and "alpha" and a joining word we eventually arrive at alphaIsTransparency Smokey is The Bandit! Job done!