I noticed there is no Make-Up Gain slider in Master-Mixer Hierarchy / Bus Property Editor / General Settings Tab. It can only be accessed using List View, or in RTPC Tab, or by selecting the parent Bus and looking at Content Editor to see the child Bus' Make-Up Gain.
It would be useful to have a slider in Master-Mixer Hierarchy / Bus Property Editor / General Settings tab, just like in Actor-Mixer Property Editor / General Settings tab. Why is that value hidden when working in Master-Mixer Hierarchy? It makes it kind of clunky to access that value.