Is your feature request related to a problem? Please describe.
Many telemetry objects may be discrete events. For example, when a command is issued, or a warning is raised. These currently cannot be visualized with data in plots.

Describe the solution you'd like
A single vertical line per discrete event, plotted along with numerical telemetry data. Some ideas include:

1. Creating a new widget in the TimeLine object to display these events.
2. Adding discrete event telemetry sources to plots.