Funny you should ask.
Before I published, when I had young children and time was at a premium, I was genuinely frustrated that I couldn’t physically work on more than one book at a time. So the most honest answer is, No. Of course I can’t type one story and dictate another.
But I often have different books in various stages of completion. I might be writing the first draft of one and have to stop for a few days because I have revisions or copy edits on another. That’s very common.
With On The Edge, the heroine, Glory, writes a book. I pretty much wrote her book, Blessed Winter, in real time as I came to points in Glory’s story where she could steal away to the cafe or whatever. I wrote it as if it was a subplot of the main book. (It kind of was.)
It was very challenging and that’s why I didn’t do it again with the next one in the series.