Check out Ginger brand towel bars. They are excellent quality, far superior than the local HD store. I have the Ginger surface collection which are modern. I got them at plumbtile online store at huge savings. I used two 32” towel bars stacked in a large master bath. Each 32” bar holds a bath sheet towel open flat to dry. Ginger has lovely traditional bars too. Celebrity cruise ships uses this brand in their ships. That’s where I saw them and had to have them. 😎

Is there another place where you can put a towel bar - say behind the bathroom door? One on the wall, and one behind the door. I assume there are two of you needing a towel bar. That's what I had to do in my kids bath. An 18 inch towel bar is not really going to do much to help the towel dry.

Why don’t you use double towel bars? I used them in a previous house and they were very useful. I used them in our master bath and guest bathrooms.

Here is a Rohl Double towel bar - I have 2 of these in my master - We don't put two towels on these, but it could be an option. However, It's not easy to get the back towel on. https://www.afsupply.com/rohl-u-6945stn-31-5-inch-perrin-and-rowe-double-towel-rail-in-satin-nickel.html?gclid=Cj0KCQjwy6T1BRDXARIsAIqCTXrKBl3E-4bHApky-CsM0PZ5aW_dMjhlQ1nxCe0DI2HSSr633Ej_V7caAiEjEALw_wcB

We put double bars in both bathrooms of our old house. In fact, in one bath we had two, one above the other, on a 20" wall. On the side wall, for hand towels, we put towel rings. They don't take up much space, and the towels still looked good when they weren't neatly folded.

Thanks everyone for the comments. I’m going to try a 30” bar. Seems like it should be enough, or I can make it work. And thanks for the reminder on the double-bars. I’d been concerned that the towels wouldn’t dry. Maybe not a problem? Thanks for your help!