Thanks for the suggestions @stucork . The Column Panel does work but as I can see it lacks the left alignment feature. The reason I wanted the Flow Panel is that if you hide the left most Linear Panel, the other two will re-position themselves to the left, this does not happen with a Column Panel.
I ended up abandoning this idea of using an XY Panel and used a Grid Panel and then programmatically set the position of the panels if one of the panels was hidden. It seems to work pretty well with cards of different lengths and using multiple filters…
Grid Panel for the win!!
