It would be nice if adding a tree to a project would run in the background so I can get on with configuring the project and not have to wait for it to finish building the list. It would also be nice if the tagging of those new files ran in the background as the title bar on the status dialog seems to indicate; "(to be completed in background)".
It just took about half an hour to add 91K+ files to a project and I will be adding a dozen more similarly sized projects to the workspace.
You can run a second instance of slickedit to configure "other" projects and do other things - use the +new switch when you invoke slickedit. If you're going to make changes to your configuration/ option settings, you need to make them in one instance of slick only and close that instance of slick last. Alternatively, use a second configuration folder using the -sc switch when you invoke slick - use options export/import to copy your settings.
You can also use 12 instances of slick to add files to your 12 projects and do the tagging in parallel but the total elapsed time will probably be longer than doing them one by one, at a guess.
I wonder what kind of project has 90000 files.
