Hello Nathan R. - Thanks for the report! Unfortunately, however, I was unable to reproduce this issue on my end. To attempt to reproduce, I start out by creating a Simic Barbarian and I choose the Manta Glide enhancement. After that, I use the Level Up Charactermancer and choose to add 1 additional level of Barbarian and then multi-class 3 levels of Bard (muscled musician for the win I guess). After choosing those class levels, when I get to the "Features" tab, it lets me select my additional enhancement and I selected Acid Spit. I was then able to complete the Charactermancer and my character seems to have both enhancements added correctly. Did you go through a different workflow to reproduce this error? If so, would you mind further describing what that was, please? Any additional information you can provide is greatly appreciated.