Problem adding the override

I am using Grafana version grafana-7.5.7 connected to InfluxDB and Jmeter
I am trying to create a panel which will contain two queries so that graph will show two lines.
So I took this dashboard (JMeter Dashboard (3.2 and up) dashboard for Grafana | Grafana Labs) and duplicated the panel called Active Threads. Then I added a query that I took from the panel called Response time.

After that I added the override → Fields returned by query. But it shows only query B

Could you please tell how is it possible to add multiple series in one graph panel?