1. Make a note of the Bound To name for the combo box and delete the combo box element from the form.
2. Save the form.
3. Use the Layout Element Adder to create your Text Box. When you do so, from the Bind Element To dropdown, instead of selecting New Text Field, select the Bound To name of the combo box.
4. Save the Form.

You now have a text box that displays the same data that appeared in the combo box.

Note: If there is programming on the events of the Combo Box, it will be deleted when you delete the Combo Box, so export your programming first, if you need for the new Text Box to run any of the same code.