Display Individual Portfolio Pages in Mobile Menu

I have a series of portfolio item pages I have nested underneath one 'Services' Portfolio Page, so that the individual item pages are organised  'services/slug.' 

I'm using a pop-out style Mobile Menu across all screen sizes, and I'd like the individual Portfolio Pages to show in that menu, instead of just 'Services' so that it's easier to navigate.

Alternatively I could use a Folder, but that also looks a bit bad on mobile as it has an arrow through instead of showing the pages.

Does anyone have know how to display the individual Portfolio Item Pages underneath the Portfolio Page?

Thanks for your help. 

Hello Badge20,

I found this solution that worked ok for me, but then you loose the "first level" menu.

I haven't figured out a way to show everything yet. Maybe you can give this option a go.