Editing Text Version in Campaign Standard

I was recently in a webinar where it was recommended to have more descriptive text versions of marketing emails, since some AI summary tools use the text version to find relevant details. In Campaign Standard, I switched off Sync with HTML, edited the text version to be more readable than the auto-generated version, and sent myself a test. However, when I view it as a text-only email, I’m still seeing the auto-generated version.

Am I unable to edit the text version through ACS, or what steps should I take to edit the email. I’d like to make sure that it includes our “view in browser” link as well as the unsubscribe link? I want to create a text version that highlights the best offers from the HTML version.