Non-hierarchical relationships

I'd like to have some way to define relationships between two requirements that are of the same type for practical reference without impacting traceability. The idea is to just create helpful references between requirements that are related to each other in content.

For example, I might want to link two together that could be overlapping in content or that give context for each other or something like that.

Sometimes using sub-items makes sense, but sometimes they are reqs that we've organized in different folders and don't want to have to nest them like that. I also don't know if regular relationships make sense since those are also hierarchical and I'm concerned that they may impact trace views or reports undesirably.

Is there a way to create non-hierarchical relationships? Or at least relationships that don't show in traceability views & reports?

For now, I'm just having to put a link on each item to the other via URL, but that's cumbersome and only one-directional unless I do the same to both items separately.