seqdiag text on activity or note without edge

[hoj]

Hello,
For a sequence, I'd like to have text on the activity line like:

+----+
| E1 |
+----+
   |
 |text|
   |
   ...


Is there a way to do this with seqdiag 0.9.0?

If not, would it make sense to implement this by adding text to node_activity, or by allowing a centered edge note without an edge?

Thanks!