Camden as water agent

Tried adding camden as "mash" so that i can get a breakout on how much to add to water prep.  1 tablet is good to treat 20g of water for chlorine so for a 5 gal batch when i prep 10g of water I only need half a tablet.  When I add 10g worth of custom water it ask to add the salts to get the desired profile which is great but I can't include the camden or sodium metabisulfite. 

So my only way to get this in is to add it as a water agent as "misc".  My categories here are either mash or sparge but not "both" if it want to treat my entire HLT volume at once.  I can add as Mash but then it only wants enough of a tablet (1/4-1/3) to treat the mash water... and i have to add another camden as "sparge" to get the rest of the water.... but it still won't equal the full 10g i'm trying to treat as actual water vols are just below (9.2-9.6gallons).

It would be nice to be able to add sodium metisulfate or camden tablets to the water profile so that when adding any volume of water to be treated I can get the exact amount.  With tablets it's not such big deal, but as i switch to powdered metabisulfite it would be nice to get exact amounts.

Id be curious what others are doing, besides just remembering to add half a tablet or a whole one at brewday.

Thanks,
  I don't think I thought of that particular use case but I will make a note to correct this in the future.

Brad