Describe the feature
when adding a pattern via the + button from JEI, stacks of the exact same item should be combined and empty slots should not be transferred.

Reasons why it should be considered
could be considered a bug with a feature.
for many non-vanilla crafting mechanics, in particular extended craftings tables, the number of individual slots for inputs are greater than 9. this makes it require entering most items and their actual amounts in the recipe manually instead of being able to properly use the + feature.
additionally, empty slots should not be transferred, as some recipes (eg extended crafting, blood magic) have empty slots in their recipe, which are currently encoded as-is, leading to multiple empty slots while the rest of the recipe remains untransferred.

Additional Context
issue first reported at p455w0rd/JustEnoughEnergistics#7, and there is an open PR on the repo (since early 2020) containing a fix (owner of repo has had no github contributions since late 2019).
another implementation of this, by NotEnoughEnergistics for 1.12.2: jei/PatternRecipeTransferHandler.java#L81