Edit multiple meshes at once? I want to edit a game model and I can't join the meshes with CtrlJ because the model will not work in the game anymore. If I use P in Edit Mode, the meshes will split into even more meshes than before, with different names, and it will not work anymore.

The model is separated into multiple meshes.
I can edit the vertices of each mesh, but I can't edit multiple meshes at once, so that they stay "synchronized".

Any idea how to do this without CtrlJ or a way to "unjoin" keeping the same meshes names before joining?
There is an addon called MultiEdit, that will enable you to edit multiple objects at once.
Here is the post on blender artists where the download can be found.

After you have installed and activated the addon, you just select the objects that you want to edit together, and click on the MultiEdit Enter button in the tool shelf.
Then when you are done, toggle back out of edit mode and click on the MultiEdit Exit button.