Heya!
Yes, you can leave your table at any time, however be aware that your merch on it will then be free for all unless you have someone to keep an eye on it
Also artists trying to get a table themselves may note your prolonged absence and complain.
Of course you can't just take a bottle of water or some food with you and hide it below your chair out of sight for hotel staff and have a snack or drink every once in a while. Nobody would do that. Never. Nope. After all, we're in a hotel where we can get nice drinks and snacks from the bar, right?
I've seen artists have display racks around, as long as they don't bother the people next to you or fall on some unexpecting guest, they should be just fine =D