@AVaughan Fuel cells are, for sure. Scrubber I'm not sure, but I did a test with a new game, using cheats to have a lot of science right away, and researching most of the three up to the elssc, but still I couldn't configure anything.
Adding to that, if I right click on fuel cell or an elssc in the VAB parts lost to check the part's info, it shows me all the possibile processes, but it says it's not reconfigurable, but that might mean I can't do that on flight, so I'm not sure if it's related.