Maybe I’m the last person to discover this but… if you quit FCP X using OPTION-COMMAND-Q, the next time you open it, you’ll be right where you left off. Am I late to the party? In any case, happy I found this one. 😀
EDIT: Turns out FCP X may not restore windows by default based on your OS “General” settings. Specifically this setting... HT Marc Bach FWIW, in most apps I like the setting to *not* restore windows, so glad to discover a way to override it when needed. This shortcut also works in all apps that respect the system settings. (Pixelmator and others)
Final Cut Pro X Babbling 
This is awesome.
Hmmm… I’m trying to figure out how this actually differs to just plain quitting? (something you can do in ANY app btw) As far as I can see I’m exactly where I was after quitting FCP normally as well. What am I missing? 🤨