Doable dropdown?

I am a UX designer.  I gave a design specification to my Mendix development team that wanted to do something like this (see below). There are headers to group each section which aren’t selectable themselves and have a different font-size and weight.    They are saying this isn’t doable in Mendix.   I have to believe something like this can be built.  Please help.
1 answers

I *think* you should be able to create something very similar to this with the Dropdown Container widget from the appstore and some styling work.  You can find that widget here: