We would very much encourage Striking Theme to support an optional possibility for Portfolio Items to be able to show the content of a specify (created) category on pageload. As of now the default "All" category is the only option.
? The portfolio shortcode supports your selecting the portfolio that you wish to load by category or id, and have only those that you selected loading. Did you try that?
Yes, I am doing that already. But I would very much like to be able to select which of the categories content to show on pageload. As explained "All" content of all selected categories will show on pageload as it is now.