How/where to adjust "Knobs".

[OranguTech]

This seems like a basic thing that I can't find any documentation on. I see frequent mention of various "Knobs" that can be tweeked, and can find them in the source -

So if I want to try EnableProgressiveRetryBackoff, I need to set an Environment Variable AGENT_ENABLE_PROGRESSIVE_RETRY_BACKOFF to TRUE? Presumably this has to be for the env that the agent itself is running in correct? Is there any way to modify that on-the-fly/from within or a pipeline run or does that mean you have to shut down an agent, manually set vars/re-start agent from a live terminal session? (Or do you have to (re)register an agent every time you want to turn a knob?)