I always have problems knowing what ingredient should be used for a base when the first set of ingredients enters the Multi Mixer. The problem is even more severe when setting up the production line before the ingredients reach the Mixer. Is there a way to know beforehand what ingredient goes where in the Multi Mixer UI?
My Suggestion: When the first set of ingredients enters the Multi Mixer pause the machine, make a popup (like the “Name Your Drug”-Thing), show both possible results and ask the player what result they want.
I think that would be a nice Quality of Life Feature. 
That sounds more intrusive than it needs to be. It would be better to just have different colored inputs and have that reflected in the gui. Instead of a black background for the 2 drugs to be mixed, let the top half be green for the green arrow input and the bottom half be yellow for a yellow arrow input.
I had a problem with this myself until I realized the the multimixer input next to the yellow/orange motor is always the top ingredient.
Since then, I’ve been able to predict the resulting ingredient, and plan accordingly.
To modify the suggestion then, perhaps it should just be made clearer when introducing the Multi-Mixer which input is which.
Perhaps a second series of tutorials for the more advanced machines?