When joining data sources with lots of attributes, it can be a little difficult to track what came from where. One potential solution would be to be able to add a coloured tag based upon the input. E.g.
How are you imagining this working, perhaps a setting in the transformer where you can set Left Unique Colour and Right Unique Colour?
Yeah, guess so? You can default to none/none then have the FME colour widget available for choice. Basically, as long as you support accessibility re: types of colour blindness, we’re all good.
TBH, it could be a ‘L/R’ label. But a colour seemed preferable to me because it is less clutter and more instantly comprehensible. YMMV.