I am no maintainer and I do not deal with a lot of issues at a time, but my guess is they systematically work through the issues. They just start with the most important ones and work on them one-by-one. That's also how pilots work through critical situations with lots of simultaneous input factors and stress ;)
Some weeks ago I saw a really nice link about zero-bug development here on Hashnode. I think it is one way to deal with stuff.