Stacked plot should better inform user how to edit plot options for telemetry

[davetsay]

Is your feature request related to a problem? Please describe.
To edit a plot series in a stacked plot, you click on the plot in which to edit. If you are unaware of this, you may not think you can configure each individual plot.

Describe the solution you'd like
The Plot Series section of the Config tab should always be present, and should display helper text if you are not selected on a specific plot.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Plot Series options appear for stacked plot config tab once you click on a child plot.

Not super clear if you haven't clicked on a child plot that clicking on a child plot will provide more options. Some verbiage would help.