Each submodel is stored only once in the main file so the only operations you can do with them are those you can do with parts: put them at some coordinates and rotate them. And select the color (used for a color named "inherited"). Nothing else.
If you want to modify them in different way you have to break this link to the same submodel. Select one instance, click right mouse button and in the context menu select "Reorganize" -> "inline". All parts of this instance become a part of the main/current model. And they stay selected so you can even move them to another submodel then, if you wish.
If you want to modify them in different way you have to break this link to the same submodel. Select one instance, click right mouse button and in the context menu select "Reorganize" -> "inline". All parts of this instance become a part of the main/current model. And they stay selected so you can even move them to another submodel then, if you wish.