I usually write in Scrivener and then paste it into Tapas, so I don't run into this problem. 
If you don't have something like Scrivener, you could use google docs or any other word processor to draft in, then move it over to Tapas when you're done. The only problem is if you use italics or bold because it doesn't copy over. There is a workaround for that, but it's a little clunky... 