ROS2 rqt_plot plugin does not allow to select topics

[WaldoPepper]

I am using rqt on a virtualized Xubuntu 22.04 with ROS2 Humble and see topics listed, but can not select them for plotting (observed on several different installations): the '+' button is greyed out...

I activated debugging but got no hint about, what goes wrong. I tried both MatPlot and QwtPlot.

[roncapat]

You may try to use a "Topic Monitor" view and drag-n-drop message fileds of interest in the plotting region.