Hi Michael,
I do agree with Tony, it needs some sort of visual separation.
Outline border sounds Ok, I thought you would have kept with the same theme and action that you have for the main icons, meaning the whole row highlights with that cool graduated blue and outline, even if you left the organisation tree plain and mouse down with that highlighting method, it should work. I'm just visualising this as I'm mousing over the icons so I don't really know how it would feel over a bunch of columns.

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