Textfield that is dependent of dropdown values

I am trying to duplicate the below pic I have attached, that exists in this screenshot I attached. It is on the Tasks Module in the Edit view. I just want another right below it on the Task module. I can see it in Studio to clone it or I am overlooking. I have not been succesful in trying to recreate it. Can anyone report to some resources that will help me to do this specific task or explain how to achieve this?

*The dropdown will only include modules we have.
*When the user selects a module from the dropdown and click the arrow next to the textfield, the ‘listview’ for that module should appear and allow the user to select something.

If is not already apparent, I am just starting with the development stuff for SuiteCRM, but I do have development experience

SuiteCRM Version 7.1.4
Apache Version 2.2.31
PHP Version 5.4.45

Thank you so much for any help you can provide!

I have used the Developer Tools of Chrome and found the element and the onchange events for the textfield and buttons in the picture I attached. I have also searched editviewdefs.php in custom/modules/Tasks/metadata, but I don’t see the buttons or text field, I just see the labels for the view. Could someone please help me on this?