"Add Related" on Task needs a TSER link
One answer
You can find the links available in the default implementation here.
https://jazz.net/help-dev/clm/topic/com.ibm.team.concert.sdk.doc/topics/r_link_domains.html
There are three artifact types in QM that you can add as "related" to , but TSER is not one of them. Unfortunately it is currently unsupported for customizing such links yet.
https://jazz.net/forum/questions/176252/how-to-create-a-custom-link-from-ccm-to-rqm-work-item-test-suite
https://jazz.net/jazz/resource/itemName/com.ibm.team.workitem.WorkItem/217250
https://jazz.net/help-dev/clm/topic/com.ibm.team.concert.sdk.doc/topics/r_link_domains.html
There are three artifact types in QM that you can add as "related" to , but TSER is not one of them. Unfortunately it is currently unsupported for customizing such links yet.
https://jazz.net/forum/questions/176252/how-to-create-a-custom-link-from-ccm-to-rqm-work-item-test-suite
https://jazz.net/jazz/resource/itemName/com.ibm.team.workitem.WorkItem/217250