This can be seen in the Recipe Ingredient report.
To do this simply open the recipe, click Reports, the Recipe ingredients will be displayed.
The recipe appears with the quantities. To obtain percentages, click the vertical ellipsis icon symbol to show options and click Express as percentages.
Ingredients in sub-recipes, if present, are given as percentages within the sub-recipe itself, not the main recipe.
To revert to the original quantities, click on the vertical ellipsis symbol again and click Revert to Quantities.