honest, I don’t have much use for a way to adjust the alpha (not by itself that is)
What would be better imo would be the option to export 1 single item, independently.
This may sound completely odd, but if you can export that specific item, then you can adjust its alpha separately, and then reinsert it with another program.
But there are also plenty of other options.
Like placing 2, 3, 4 etc… of the same items in the same pic for instance
So this may be a win/win option.