JSitemap supports different priority value for each data source.

Inside the data source edit mode you can change the value of priority using the dropdown to assign a higher relevance to some items on your site and emphasize them for search engines.

Moreover using data sources of type 'menu' you can also assign priority for every specific menu item. In the edit mode of every single data source related to menus, you will be able to control priorities using the dropdown controls in the bottom part of the screen.