Modify Meta Description manually

Hello,

I’m developing a website using Elementor with Astra Child Theme and I want to change the Meta Description manually.

I understand that it captures information automatically from the excerpt or another chosen field.
I could modify the excerpt I guess, but unfortunately, I don’t see an active excerpt field even though it seems enabled in the Astra settings.
Is there any way to modify that text manually directly on RankMath panel?
Or, is there a best practice that you suggest to populate the meta description (eg creating a dedicated ACF field)?

Thank you very much for your assistance
J.