Similar in function to setting the title of the current document to the selected text. Cmd-Opt-Shift-Y looks available. This action would replace the current synopsis with the selected text.
I second this. I never use the Synopsis field simply because it’s too much trouble to go back and fill it in after writing (I know, I know, it’s for outlining).
Or, how about if there is a selection, this is used when the three dots button is pressed?
That would work fine for me, though a short cut would be nice . But your solution would at least eliminate the need to first select the “-No Synopsis-” text and then copy&paste or drag text into the card, which is currently a bit of a drag.