Good news, Jeff - this is now live 
Recipe steps can be marked as Optional, and an optional ingredient addition can have a quantity of 0, so there’s no need for the 0.0001 workaround any more. Mark the ingredient addition as optional in the recipe, and it will accept a quantity of 0.
On the brew sheet, an optional step you don’t need can be marked as Deliberately skipped, so it’s clear it was a decision rather than something forgotten.
Jacques-Marie, this also covers optional actions such as an extra rest or an enzyme addition: add them to the recipe as optional steps and skip them on the brew day when they aren’t needed.
This came as part of our new production tasks release, which you can read about in the announcement. More detail on optional steps is in Recipes & brew sheets.