Just so I'm clear...the copybooks are in PROJECT2, which is a remote, linked project? And you are opening a program from PROJECT1 and trying to do "Go to definition" on a copybook symbol, which is defined in PROJECT2?
If your linked project was local, you would just set the copybook search path in SlickEdit to contain the path or paths where your copybooks are located, which is easy to do. We don't currently have the facility however, to automatically retrieve copybooks from remote locations...so this isn't going to work for you

. I think you are going to have to manually open the copybooks from the linked project.
We have a few feature requests filed to make our tagging and searching work more seamlessly with linked projects, and I'll add your information here to one of the requests. Are you using RDz, Compuware Workbench, or any other 3rd party Eclipse-based IDE?
- Ryan