sublime text 3 on mac os not keeping project open

As far as I'm aware, you can't have a set of project folders automatically open after closing and reopening the Sublime Text window (this has something to do with OS X memory management). However, if you have a lot of folders to open, instead of dragging them one by one into the Sublime Text window, you can do the following (which saves lots of time).

1. Open Sublime Text and add folders by either dragging them into the window or opening them by going to Project > Add Folder to Project. They should appear in the sidebar.
2. Go to Project > Save Project As... and choose a directory to store your project information.
3. You can then Project > Edit Project or Project > Refresh Folders if needed.
4. The next time you close and reopen your window, you can quickly re-add all your projects/folders by going to Project > Recent Project and clicking on the only available project.

Although this way doesn't open the projects automatically for you, you can get back up and running in one or two clicks.

Follow this guide here: https://stackoverflow.com/questions/25753743/sublime-text-3-on-mac-os-not-keeping-project-open

The main thing here is to close Sublime after adding the project folder (properly close it) by select Sublime and Quit.

This should then remember your folders, without having to specifically save them as a project