I believe Sandal IS the Maker.
I also think Sandal is June, the elvhen god of craft / making stuff. And Sandal is The Stone, or perhaps The Stone's soul. Since little is known at all about June or the Maker, I'd also suggest Sandal is The Tevinter's Maker - with one codex explaining that when the Maker turned his back on the spirit world, demons grew from jealous spirits. We never see Sandal in the spirit world, only in the real world.
I would not be surprised if the little enchanter created everything.
Maybe I'm wrong. But there's a big reason why Sandal has been no where near Solas or Inquisition except as a Cameo.
But wouldn't that be sweet? If the Maker chose to manifest as a sweetheart dwarf? Not intervening, just watching his creations in his world and offering help when approached.