Watchlists are similar to portfolios - the difference is that while portfolio contains other data about each entry, a watch list is just a simple list of symbols.
Because of that, a watch list has an extra Symbols section in the Main tab of the ribbon menu where you can add or remove symbols from the list, or just replace the list with another list. It also does not have Totals or Sub-totals, since it has no information from which to calculate them. If you insert a separator symbol (three dashes - ---) in the list, you will get a collapsible Sub-group.