I've looked for this but it doesn't seem to exist. I've found myself needing this quite a lot recently. At the moment I'm going to project settings and 'Subtract cursor position' from the project start time, which is absolutely great if a little fiddly, and it would be nice to *hit button*->0:0.000
perhaps "transport: go to start of project" if not then you could be sneaky and put a marker there (if you have negative time before zero or your project doesn't start at 0.
You might even be able to right a reaconsole command for it and assign it to a key.
Indeed, thanks musicbynumbers but it's not quite what I'm looking for. Rereading it, it wasn't very clear!
Yes, I click anywhere, press a button and it makes that point on the timeline 0:0.00. So everything before it is negative.
Reascript is indeed a possibility but I must admit I haven't dared open that box yet... maybe it isn't so scary. Being able to bind the 'Subtract current cursor position' button in project settings might help with chaining actions. I'll FR it if it's thought of as useful...