And on the other properties it takes place . Otherwise there is still the solution to open another MEP and see if they take place there. If so, you can select them all and copy them to the other MEP. In fact, it all depends on your customizable settings in your MEPs. In ours, it doesn't happen. All custom properties are in the room.
For example, with a part, if we remove the properties file in the lang/french folder, then we will no longer have the drop-down list. but I don't know if there is an identical file for MEPs.
If you remove this file it will apply to all your plans. Since it's in the SolidWorks source file. And for the MEP one normally we create the properties with their links when creating the basemap.