Secondary categories one line

(THIS WAS POSTED IN WRONG CATEGORY)
Hi there,
What file would I edit that contains the secondary category search box that shows when you edit an item on the frontend? screencast.com/t/EscVMXql

I want the search bar to be to the left of the item and each category an item is in to side by side instead of one on top of the other. I'm hoping by editing this file, I can accomplish this.

Thanks!

Hello

the selector is select2 JS

you can try using CSS

use:
#the_name_of_the_container ... .someclass {
}