Edit an entire group

Is it possible to make it so that an entire group of objects can be modified altogether? For example, if I have a group of spaceships and I want to add a new variable to them all (e.g. attackspeed), it would be easier to right click on the group “spaceships” and add the variable and have it automatically added to all objects in that group.

I don’t think so.
For my own project I used an invisible object as a workaround. The object holds the variables which are shared by “the group”. I then link (Linked objects extension) all instances to that invisible object in order to be able to retrieve the information.