You can change the entity class with the command: 'GPLACER_CLASS class_name' You can move the props, remove them, or add new ones and updating with GPLACER_UPDATE will reflect these changes in Hammer without creating multiple versions of each prop. To send all placed props to hammer, enter into console: GPLACER_UPDATE The map file's name name must be the exact same in Hammer as it is in Gmod! Furthermore, this will only work if you are hosting the game off of your computer (singleplayer/listen server). Hammer and Garrysmod must both be running at the same time and Steam must be running as administrator. While in Gplacer mode, all props you spawn will be marked as being Gplaced. To enter gPlacer mode, enter in to console: GPLACER_TOGGLE I don't do much mapping, but from what little experience I have, I definitely know that I much prefer building and placing props in Gmod over trying to meticulously place them in Hammer. A little tool meant to make prop placement easier for mappers by allowing you to place any prop in Gmod and push it to hammer.

Gmod file stealer 2018