A couple of other options you can play around with is to save each cover to your story, and create the highlight from that, and save it as a cover. Or, you could create a single all over screenshot right in your Instagram story, use the tools within Instagram to add text, emojis, or pictures and save those as highlights and edit as covers.
Do you like this quick tutorial? Is there a way I could make it easier or clearer, perhaps a video screen recording as I go through the steps? I really just play around with it until I figure it out, so going step by step is a challenge for me, so if I left something out, please comment below!
Have fun!
Anne