Is it possible for a Gatling journey to contain branches or to stop at certain steps with a given probability? I've had a bit of a look and it looks like journeys are static but I can't see anything obvious to say that these things aren't possible.
Looks like it is possible with Gatling's doIf, doIfEquals, doIfOrElse, etc. See https://docs.gatling.io/reference/script/core/scenario/ for details.