We could have an extra button called "Replace" next to the "Add" and "Remove" on all places where this is a feature (triggers, actions, etc).
So instead of having to remove one condition and then click the + to add a new one, we could have a 3rd button (let's say a yellow one with a different symbol) that would open the same menu with all the different options and it would replace the current condition with the one we choose. It's just an extra step that could be removed.