Hedging because things do change every year, so until we get the rules & rundown for this year (and heck, more accurately - until we see how the first night/day goes), we won't know for sure. That said:
- In the past, there have been overnight lines in the basement of the convention center. Previously they had separate lines for that day's Hall 23 panel and the show floor (merch/smaller panels), and they've also done separate lines for Gold Members for Hall 23. Again, not sure what it looks like this year
- Lines are safe, there are restrooms, it's just really, really cold with a hard floor, so folks come prepared to wait it out/sleep. Some years they even have TVs near the lines playing Disney movies
- Last time I went overnight was 2017 - I got in line for the show floor around 9 PM on Thursday night (entered the basement, went through security, and was able to bring my pillow back to the room around 7 AM on Friday before they took us upstairs). In 2019 I had a sorcerer badge & didn't need to do overnights, but saw a few folks lined up outside as early as Wednesday afternoon (typically scalpers, other merch seekers). Their small unofficial line was forced outside the CC grounds, so they moved it to the sidewalk. I don't know what happened when the CC opened for overnight lineups, but I assume they were near the front.
- At some point, they cut off the basement and start security lines outside the CC. People in this thread and on FB will usually give real time updates. And typically by the afternoon there won't be long lines to get in - just lines for merch, panels, and experiences inside
I'm not sure if they're going to want throngs of people in the basement overnight. That's possibly why they'll do pre-reservations and use the
Disneyland app for store queuing. TBH, I'm considering updating my phone to ensure it's super fast before Expo weekend so I don't miss out on any of the store queues. I've been really lucky in WDW, but didn't get a Guardians VQ for the first time a few weeks ago and it's made me nervous.