Multiple lists not possible in a single pane, but grouping list items is. Check out Sanity's documentation.

Is it possible to have multiple lists in the desk structure? E.g. a list with title content, and a list with title Settings below.

what do you mean multiple lists? you can customize with grouping listItems however you want, I have a settings list that itself is not an object nor document, just for grouping setting documents

If you mean adding multiple heading/titles in a single pane and list items under each one, then no, this is not currently possible with the current API. But as Cali said above, you can have multiple list items in a single pane that opens different lists in child panes. You can find more info about how to do that and how it looks like here: https://www.sanity.io/guides/getting-started-with-structure-builder