Scrollbar can be inserted into "checkboxes" type  attributes?

@kriskoyk
Probably yes by setting max-height and overflow-y

In which file are these settings located?

It's css / stylesheet.

I added to user.css on line 10 here: #atr-search > :not(.atr-subtype-boxed) ul.atr-ul {display:block!important;border: 1px solid #aaa;  padding: 6px 8px 6px 8px;max-height:200px;overflow-y:auto;}  the " border: 1px solid #aaa; padding: 6px 8px 6px 8px;max-height:200px;overflow-y:auto; "

and on line 82 here: #atr-form .control-group > .controls {display:inline-block;max-width:72%;margin:0;position:relative;border: 1px solid #aaa;  max-height:200px;overflow-y:auto;} the "border: 1px solid #aaa; max-height:200px;overflow-y:auto; which was not there and now works fine

Are these movements correct?

How can I make this box popup?

This cannot be done just from paper reading your CSS and from head just guessing what should be done.

Are you talking about the popup box?

Are the other moves I made correct?

@kriskoyk
Lol dude, you need to apply those changes to your live website and see if it works as you want...

CSS = visual design. You can't just write it here and expect anybody to understand what it does or what you mean.