Add series

I have an issue when I want to add series to a graph on a dashboard. The proposed questions to add depends on which charts I start from. I have 3 series : A, B and C. If I choose C first, then I can add on top of only B, but if I choose B first, I can add A and C. The problem is that i need to add them in order to get the legend in order too. Moreover we cannot change the order afterward. Is there an explanation to that ?

question metadata, it seems that's not compatible

which version are you on?