Created attachment 110979 [details] screenshot K3b 17.12.2 on Arch Linux, See screenshot.
Same thing with K3b 18.04.2 on Arch Linux.
Steps to reproduce: 1. open K3b 2. click on "More actions...' and choose 'New Mixed mode CD project' 3. add audio and data to your project 4. click on 'Burn' button 5. click on 'Misc' tab
Fixed in K3b 23.04.2 by https://invent.kde.org/multimedia/k3b/-/commit/98462e91d7f6bf0de1b2832cd0106b49d65938f3