Is there a way to add a specific modifier to more than one object? I know you can copy the modifiers after adding it to one object, but is it possible to add one specific modifier to many objects at once?

For instance, I have many objects with different modifiers and I want to make them all collision objects. If I use CtrlL it copies all the modifiers on the active object to the selected objects. I only want to add a collision modifier to the existing modifiers.

Is this possible?
As I experiened, the Copy Attributes Menu addon can well support this. You can find Copy Seleced Modifers down the menu, which will only copy sepcific modifier(s) without replacing the original stack. Hope it helps.