Dear bharatB,
in CRED the select field that is used to display hierarchical taxonomies fields, like for instace the WP default categories, doesn't appear as an input box so not allowing for insert text and filtering the content.
You can click on the select and type the desired taxonomy this will make the select highlight to jump to that option.
Please let me know if you are satisfied with my answer and if I can help you with any other questions you might have.
Regards,
Ana