When changing "Position of sensors table" the graph is frequently lost ...

[watmough]

When changing "Position of sensors table" the graph is frequently lost. User must work out that there is an invisible splitter that must be dragged to display both graph and table.

Suggestion:
Prevent the splitter from being fully left/right/top/bottom so it can always be 'seen',
Or, allow a both or single panel display, selectable through a radio button in preferences, [and reflect this after splitter drags]
Or, probably best, implement a legend inside the regular graph, which would now take up the entire window.