It seems to me or am I just missing it. The filament diameter is being set in the "Other" tab one time, however it is possible that 2 different filament diameters are going to be used. My support filament is 1.75, but the primary filament is 1.65 in this case. Quite a bit of difference.
So the feature request is to move the filament diameter, cost and density to the extruder pane so it can be set per extruder.
Second related request would be to calculate filament cost and usage separately for the left vs right extruder. Of course this only affects dual extruder capable machines which a lot are not. But for the ones that are I would like to know my actual filament cost for the supports, and actual cost for the part. Actually to go a step further, if only using one extruder, I would like to be able see how much the filament costs for the actual part and how much filament is being used for support and the cost.