I have simple moving average charts for bond yields. For certain tenors (e.g., 3 month, 6 month, etc. bill rates) there are two y-axes. One for the actual yield line and another that groups together all the moving averages (e.g., 50 DMA, 200 DMA, etc.). I tried to group them and that didn't work -- they remain segregated. To be honest, I think a lot of the charting functions have been finicky over the past week -- not sure if something changed on the back end...