Fate System Toolkit
Supplemental actions don’t appear anywhere in Fate Core, despite having appeared in previous versions of Fate. We did this for two reasons. First, we feel it’s better to use bonuses than penalties, and supplemental actions imposed a penalty. Second, supplemental actions are there to make things more “realistic,” but they don’t necessarily make things more fun or more like an exciting story. They make it harder to do cool things, not easier.
That doesn’t mean that the concept doesn’t have value, though. If you want to use supplemental actions, you can simply use them as they appear in previous versions of Fate—performing an action that would distract from your primary action imposes a -1 penalty on your primary action. Most of these actions are free actions in Fate Core. We leave it to you to determine which free actions should be supplemental actions.
If you want something that’s a little more in keeping with the ethos of Fate Core, and that doesn’t impose a penalty, try this out.
When you perform some minor action in addition to your primary action—moving a zone, drawing a weapon, ducking behind cover, or anything else that the GM deems is a supplemental action—you create a boost such as Distracted, Obscured View, or Shaky Aim, which lasts until your next turn starts. You can perform only one such action, so you’ll create only one such boost. Anyone acting against you or defending against your action can use this boost—at which point it goes away, like a normal boost. Also, the GM may compel you with it once for free—meaning that she doesn’t have to offer you a fate point, but you may still pay one to resist the compel—at which point it disappears.