This is my first trip using the Lines app. Can it handle two people being logged in at the same time? Any other tips about the app would be appreciated as well
It should be fine. My husband was logged in to the Uni side while I was logged in to the WDW side last April and we had no issues. Granted I wasn't logged in as much as he was but we definitely overlapped
Just be careful that both parties aren't making changes - that could get confusing.
Yes DM and I are both signed it at the same time and haven't ever noticed any problems. I would just see magical updates to our checklist or threads/replies on the chat.