I accidentally reset the dynamic of many channels in an orchestra work, and now I would like to set them back to the default settings which was 0.54 (BBC SO). Is there any way to do this simultaneously on all channels?
No, I’m afraid not: the only way to do this other than Ctrl+clicking or double-clicking each fader would be to reapply the playback template. That might be quicker, provided you’ve not made any other changes you want to preserve.