Choose dataset properties in PropertiesPanel

I noticed that some kind of datasets have multiple properties listed in Variables panel.
E.g. paraview example can.ex2:
and I’m able to choose a subset to load before clicking the Apply button. I also want my dataset(.vtk) to behave this way when loaded but not sure how. I tried Field Data but all my fields are only listed in DisplayPanel for colormap reflection. How should I organize my vtk dataset structure in order to let the PropertiesPanel work for my dataset?
Thanks for any advice.

Not supported by the .vtk format (which is a legacy format).
You may want to save your data into a more modern format, like .vtp or .vtu, which support this feature.