if somone could point me in the right direction how to change what comes up in the global search and what doesnt

Curious as well. I noticed though that it is significantly based on permissions (obviously).

When you create a custom field there is a checkbox called Global Search on the right side. Keep in mind that some field types cannot be made into a global search.

Correct I need line field fields of transfer order

This would be tough to achieve without scripting. Are the line fields you're trying to find unique on every line and every transition? Otherwise if you are trying to find a Sales Order on which one line has a Quantity Shipped of "1" then you will get thousands of results