Please go to new post or edit post, at the top right you will get screen options just click on that. Now you will get options lists to check, check to excerpt and at the bottom of the content, you will get now excerpt field. Add your custom excerpt there.
Here is screenshot:
Let us know if this helps or need more help please do reply.
I would like to ask you a favor Afterwords. Would you mind taking a few minutes to write a review for me, please?
Your comments help others know what to expect when theyíre looking for the theme we offer.
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Thanks for using our theme, Afterwords. I’m looking forward to reading your comments.