This extension turns specific text fields into select fields with customizable options from a specified Option Group. The “(Custom value)” option allows free-form values when necessary. 

Installation and Usage: 

After installing the extension, the text field will not be affected until settings are defined on the new “TextSelect Settings” page, which can be found under Administrator > Customize Data and Screens. 

Currently supports the Contribution Source field; contact Joinery to discuss support for additional fields.

For more information about this extension, see here