Yes, probably you'd have to start a new game.
I did this once while I was playing my mod, and I noticed some of the entities I put in with the editor after I started the game, weren't appearing in the game once I injected the txt files and so on. But if you modify them in the editor and you didn't visit the location in the game yet but you saved it, you maybe could see them in the location you didn't visit, this will be just one time available.
The .txt files already injected (the ones with QM, quarter master,items) cannot be modified while you have a savegame I guess...
It's all about injecting the .cam files into the game, you can't do that twice while you started a game with them.
The .cam file already injected cannot be modified while you are on the same .sav file. For example I have a very old save game from 2014 playing on xxx.mis map, I updated the map last year, but the map from the save game didn't change, thus the game is pretty much static.