You can add post ID manually, it's in address bar when editing single project.
I'm developing for non-technical people, who find wp-admin quite overwhelming - had to use a very simple frontend solution.
Full solution for this is planed to be released in a month or so.
Ah okay, I understand.
I played around with your code, tried passing a 'projectID' parameter in the url and use $_GET but it didn't work (works in single project page, but not colorbox).
So currently I (kind of) found a workaround, installed Easy Fancybox and added "fancybox iframe" into the href class in line 270+, under the //create link to single post comment. It's the simplest solution I could think of.
Probably a terrible idea lol but eh it works in the meantime. Can you update this thread when your fix is finished? Thanks.