More than 26 queries per graph: can't move series up or down

Usually queries are assigned a name from A-Z.
When there are more than 26 (Z) queries the name field remains empty and I cant move series without a name up or down when there are more than one series without an assigned letter on top of each other.
Is that a known bug?

I’m using Grafana 6.0.2 and InfluxDB.