You could use IID which is unique identifier of each instance starting at 0. So using a global variable to compare with, you have an event that always highlights the instance where object.iid=globalvariable, the first instance at IID 0 would be selected. When you press tab you add 1 to the global variable so it moves between them. You would need one additional bit of logic where gv is higher than the number of objects so that would be something like gv = object.count - > set gv to 0, to cycle back round to the first one. Because IID is kind of creation order the selection might seem random to the player but I did ask.