I found this I hope it helps you but I cannot make it work perfectely. I first tried to place another user's runway and saved it (even if nothing can be launched outside KSC). It works and keep existing for the next fly. Then I tried to build a hangar next to it with some static parts added by me using stock parts (and B9 parts) .mu. I was able to place it like I wanted (but building with this only tool is very hard lol) but even after using the save button (and F5) it dissapear every time I switch flies or quit the game. Forgive my english, I am a french speaker =)
