I've been working with support to troubleshoot why our autobalanced groups ... don't.
We use "Large" collectors as defined in the Collector Config... apparently, that breaks the expected behavior of the UI for entering rebalancing thresholds. I was provided the math used to calculate threshold against config to get the "effective threshold." I don't want to do that math, so I'm making powershell do it for me... now you can to:
#Effective Threshold Calculation : (Target_Collector_Mem/M