We had this debate at home prior to our last trip. Newly diagnosed similar type of issue and we went back and forth on whether to even attempt for a
DAS. We felt like it was legitimate, if we could wait by a bathroom it would be great.
But what bugged us was - what's the keep every potty training parent (including us) to ask for a DAS because the toddler is out of diapers but doesn't have a big enough bladder to hold it for an hour? The best answer amongst ourselves was that the toddler would technically be able to go back into pull ups. But, an adult could technically wear adult diapers. Sure there's the humiliation, discomfort, etc. But that all applies to a 3-4 year old as well.
It was a tough debate amongst just ourselves, and yes we found ourselves leaving multiple lines because our toddler needed the restroom. Disney does a pretty good job at letting you back in, but it is extremely difficult to get a cast members attention sometimes.
What we found if you are stuck, take a direct path out. That usually gets a cast members attention. If it doesn't and you get back out just go to the rider swap/DAS/FP area and tell them you left the line because you/someone in your party needed to use the facilities. They will give you a return time. Worst case, even CM in character will do the right things.
We had to leave the line urgently during slinky dog, frozen, test track, speedway, dumbo, mine train, runaway railway, smugglers run, even rise of the resistance!! That one was the most difficult and got us a backstage tour to some of the most pristine bathrooms we've ever seen.