Using Jira Plans, we know that we can link two dependent Stories together.
We see that Jira will turn the linkage colour red if Story B is starting before Story A completes.
This is a finish-to-start linkage.
Is it possible to show a finish-to-finish linkage?
I.e. Story B can start whilst Story A is still going, but until Story A completes, Story B cannot complete.
The only way I can see to do this is via a workaround - i.e. split Story B into 2 pieces; link Story A to Story B(ii) and link Story A to the "very end" activity of Story B(ii).
I hope this makes sense!