Brett S. once you export out of Relume, and make edits in Figma - the figma version becomes your new source of truth - however you can paste in individual sections or pages from the Relume Site Builder into Figma.
Its basically a one way sync since we are not able to grab the changes you made in Figma and bring them into the Site builder.
This screenshot shows you where you can paste individual sections into Figma.