Requested by users. People are used to zooming in with a double-click. New location is added as a side effect. This is unexpected.

Options:

• double-click doesn't zoom but adds a new location, single does nothing
• double-click zooms but doesn't add a location, single adds location
• right-click + context menu, single does nothing, double zooms
• edit button that activates edit mode in which locations can be added with a single click