Hello,
Thank you for contacting Rank Math, and sorry for any inconvenience caused.
Please note that some options are only available when you enable the Advanced Mode in the Rank Math dashboard:

Once done, go to Rank Math > General Settings > Edit robots.txt
Here is a guide for your reference:
https://rankmath.com/kb/how-to-edit-robots-txt-with-rank-math/
I hope this helps. Looking forward to helping you.
I had figured that out, but yes this information is useful. Thank you!
Hello,
We are super happy that this resolved your issue. If you have any other questions in the future, know that we are here to help you.
If you don’t mind me asking, could you please leave us a review (if you haven’t already) on https://wordpress.org/support/plugin/seo-by-rank-math/reviews/#new-post about your overall experience with Rank Math? We appreciate your time and patience.
If you do have another question in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
Thank you.