ARRAY/PIVOT + duplicates - need to return multiple match values

Attempting to achieve the following. Best that i show you!

multiple-matches.png

I'm most confused about the yellow cell, as there is no data validation applied. You just type the animal, and
it gives you the matches. Neither is there any formula, or it's hidden?

My table looks like this:

data1.PNG

I created a pivot table, since i had duplicate values in the "EXPENSES" column,
and i didn't want to have duplicates showing up in the data validation list ("Expense" column).

data2.PNG

If there's a better way to do it - PLEASE, let me know.

Now the problem is, that when i choose a certain expense, for example cleaning,
i want the Code column (w/ three question marks) to generate all the codes associated with cleaning.

VLOOKUP or INDEX only gives the first result. I need them all, so i have to use ARRAY FORMULA?

data3.PNG

This is where it gets tricky. I'm a beginner so this is all new to me. I'd be thankful for any kind of help!

Download my table: