@kensanata Can you not offset (a copy of) the River Curve itself (by a constant x+2, y+2, or figure out the "normal" of the river and offset in that direction), and just use that?
@jos Hm, I guess if you argued that all the labels will be short then the river segment they will be placed on might be straight enough. I’d have to give it a try with some generated river names.
@jos That only works for straight rivers. In curves, a different section of the river will now intersect the offset curve and the label on it.