Hi,
When editing a chamfer or fillet feature, it seems not possible to edit the selection of edges other than remove them all. This is rather inconvenient if you have a large number of edges and you only want to exclude one of them from your selection. Also, adding edges seems not to be working the same for fillets and chamfers. In fillets I have the option to add selection, but not in chemfer...
Anyway, an idea would be to highlight (perhaps in semi-transparent) the original edges to allow you to deselect them individually.