I have a HDA that produce two outputs. A heightfield and some geometry. The HDA produces two work items, where the heightfield is sent to an other HDA, and the second work item contains my geometry. Now I wanna set that geometry to output, so I put a ROP Output afterwards and I've named it HE_OUT_, but it's not shown in Unreal. It doesn't even get cooked.

Switched that node to a ROP Import, set to use the upstream output file as it's source. It now works.

And I had to set “Load Geometry During Cook”. I guess the node tries to import from when the very first node in the chain starts evaluating.