Hello, Jennavieve, thanks for the reply and compliment! Yes, if the NPC always returns to that same spot after he leaves the party, then I would recommend Switches instead of Self-Switches. However, it sounded like it is a simple one-time event.
In the case that if you want your new NPC character able to leave your party many times (for example) and always returns to that same spot where you have to talk to him/her to join your party again, then this is how you can do it:
First page:
1. On the left: Set this to "Action button" for the trigger, with the NPC's character sprite, and same level as characters.
2. Still on the left: make it a required condition that "Switch = OFF." To do this, you click on one of the Switch conditions (the "..." thing), and it should take you to a window called "Switches."
3. Then, on the "Switches" window, you name a Switch on the right. For example, maybe the name of Switch 001 is "[IN PARTY] NPC."
4. Then, on the right, add the events I mentioned earlier. However, instead of "Self Switch A = ON," you add "Switch 001 [IN PARTY] NPC = ON."
5. Later on in the game, for every event or time where the NPC leaves your party, you add a "Switch 001 [IN PARTY] NPC = OFF" to such events.
6. That's it, and no need for a second page!