How would i get other mods to work in the modding environment? Like if i wanted jei or journeymap for testing.
I had the same problem and found the solution here: https://www.reddit.com/r/feedthebeast/comments/4zp2ku/is_it_possible_to_add_mods_to_the_1102_forge_dev/ (by brute force googling)
Go to Run/"Run Configurations ...", select in tree left "Java Application"/<Name-of-your-ProjectFolder>_Client, go to "Arguments" Tab and remove in "VM arguments" "-DFORGE_FORCE_FRAME_RECALC=true" what should be the whole content of that textfield.
This stops FML/Gradle to use any mod in its d