If you don't want to have to bring up the dialog, you'd have to resort to using a macro. There isn't a command to repeat the last debug session without prompting, though that does sound like it would be a helpful addition. I'm not sure how much that will involve, I'll put it on my list to take a look at.
The attached source file provides a 'example_debug_attach' command whose parameters can be changed for the remote host, port and workspace name. If you edit that, go to the SlickEdit command line and type "load testfile.e", you can bind that example_debug_attach command to a key, or just run it on the SlickEdit command line.