In my mind Solid’ is absolutely not local ! It’s for the Dezentralized Web !
The app ( website / native / webapp … Or other) use data from many source…
So Spoggy4 Can Do that : plug to remote POD source or deal with localstorage, it open’s the localfilebrowser.
So, for your need, i think the functionnalities are already available,
What you’re looking for is made by the filepicker and the handlefileselected in this file https://github.com/scenaristeur/spoggy4/blob/master/src/components/solid/vis-popup.js
Agree with smag0