I'm hoping to add detail/description/note/label/text of any sort to my Relationship arrows, in order to indicate process, transformation, cause/effect, etc. The Relationship arrow is sufficient for simply associating concepts, but it's very limited in meaning if no information can be attached directly to it. 

For example:

Node 1: Bone marrow

  Sub-node 1.1: Hemopoietic stem cells

Node 2: Liver

  Sub-node 2.1: Erythropoietin hormone

Node 3: Blood

  Sub-node 3.1: Plasma

  Sub-node 3.2: Cells 

       Sub-sub-node 3.2.1: Erythrocytes (RBC)

       Sub-sub-node 3.2.2: Leukocytes (WBC)

       Sub-sub-node 3.2.3: Thrombocytes (Platelets)

Relationship arrow 1 points from 2.1 to 1.1, with relationship arrow labeled "Acts on stem cells"

Relationship arrow 2 points from 1.1 to 3.2.1, with relationship arrow labeled: "Stem cells differentiate into erythrocytes."

My point here is that without those labels on the relationship arrows, the connection - the relationship itself - means next to nothing, only that there is some association between the two concepts, but without a label on that relationship, the association can't be determined.

So, is this possible to do? Please advise. 

Thanks...