I would also like to know the answer to this question, along with the more expansive question: What, if any, are the actions that are selectable in the RM4 menus that will act on more than just the rule in which it is selected?
Basically, a few cancel/stop/set-type actions in Rule Machine allow you to perform actions on other rules. Most do not. This is apparent from the UI--for example, when using the "Set Private Boolean True" (or "...False") action, you get choices for which rule(s) you want to affect with that action:
In most cases, you do not get anything like this. For example, a regular "Cancel Delayed Actions" gives you this:
Such an action affects only the current rule.
Honestly, off the top of my head, I do not know which allow you to choose other rules and which don't. I can tell you that most (all?) that do allow you to choose other rules are under the "Set Private Boolean, Run/Cancel/PAuse Rules" category. In fact, there is a way to to effectively perform a "Cancel Delayed Actions" action on another rule using one of these actions, "Cancel Rule Timers":
As you can see, it cancels a bit more than just delayed actions (the UI spells out exactly what it does), but the dropdown at the bottom does allow you to choose one or more specific rules (including the current rule if so desired).
Someone who knows every Rule Machine action off the top of their head might be able to give you a list of exactly what you're looking for, but I hope this is helpful enough for you to figure it out when needed (which is what I do on account of the fact that I don't memorize these all ).
Cancel All Timers will also cancel all periodic triggers until you go in and hit "Done" on the rule again.
The actions that affect more than the current rule are all in that same sub menu.
Private Boolean True
Private Boolean False
Run Rule Actions
Cancel All Timers