Compile multiple CSVs and combine repeated value using multiple conditions and append the value in a new column

I recommend that you should write some code to attempt this, and come to us with specific questions relating to where you get stuck.
perhaps I can assume you know how to read_csv's. if you want to know how to iterate / do repeated operations, you should study the purrr package.
If you want to know how to manipulate data.frames you should study the tidyverse.
There are books that can help you.

Finally to get the best help from users on the forum, provide a reprex.
FAQ: How to do a minimal reproducible example ( reprex ) for beginners

Also here is general good info and advice on using this forum.