Applied a previous stash and had some merge conflicts in class STCollectionEditor and STVariableEditor. I've resolved the conflicts, but I may have to go back and change a few things if they weren't the right changes.
Changed the class structure for this project s.t. STVariableEditor now inherits from STEditor. This makes more sense, because editing the data of a QModelIndex doesn't require any real knowledge about the model it belongs to. I've taken a look at two STVariableEditorWidget classes so far (STVariableNameWidget and STVariablePrecisionWidget) and have made the appropriate changes to bring them to the new requirements.
Played with the STVariableUnitsWidget to implement new requirements.
Created new class STPlotCollection, which represents a collection of different STPlots, which WILL become the sort of model behind plot views (changes not made yet).
Repurposing STPlot as a place to store data related to a specific plot. It is now a descendent of STCollectionEditor.