Dynamic ingredient amount scaling in the instructions

[JohannesFleischer]

Is your feature request related to a problem? Please describe.
It's generally great to be able to scale the Ingredients-list with the servings count.
This is great when you use an ingredient just in one step since you can refer to it as: now add the milk

But this is no longer possible if you need to add Milk at two different steps, like for the topping and for the dough of a cake. Then It's necessary to write something like Now add 2/3 of the Milk which is quite impractical.

Describe the solution you'd like
I would love to have an option to write a scaling indicator based on the default Servings count in the text which then can be evaluated to a specific amount depending on the specified scaling.

But this notation should also be easily readable when opened with an application which does not support this feature.

A notation somewhat like this:
#[PORTION_OF_INGREDIENT, INGREDIENT_NAME]
example:

• ingredients: "1 L Milk"
• Text: "Now add #[0.5, Milk] to the mixture"
• Result: "Now add 0.5 L Milk to the mixture"

would be great, but I am quite certain that it is quite a bit more complicated than that, since this is a pretty native approach, and that you will have no problem coming up with a better alternative :)

Describe alternatives you've considered
Current alternatives are:

• Splitting every recipe with this problem into multiple parts and linking to them in a "main recipe"
  • but this is probably not possible in every case since not everything can be split into multiple distinct components
• writing fractions like 200/300 g Milk and then recalculate while reading the instructions
  • this loses the whole benefit of having the servings scaling

[JohannesFleischer]

The approach in #2985 would be a pretty clean solution I think