After seeing which voltage control files stop charging (acc -t), you can set one (acc -ss) and see if it keeps the power bank active.Correct. That is the default behavior of all power banks, AFAIK. The issue is the power bank stopping when the gadget is fully charged, requiring either an "unplug & replug" or a press of the power button to resume charging.
By the way, for time being, I think I found a workaround to keep the power bank active. I set max current to 500 mA, and max voltage to 3900 mV. Although the profile is 5/85/90 (off/resume/pause), the phone's battery has been showing 77% and charging for the past few hours. It does show as "full" under battery settings and "charged" on lock screen, but as long as I don't have to go and press that button, I'm good with it until some good soul suggests a better way.
Any switch that supports idle mode for that matter, should keep the power bank active.