There are two problems (maybe related ?)

1. Adding custom classes or attributes for embedimage prevents the editor to be displayed
[Seems to be a problem of config name... See below comment 26/sept/2022]

2. Classes or attributes defined for embed are not accessible and can't be edited... the pencil icon remains grayed out... I also don't have any popup like the ones that are displayed when clicking on an embedded image or a link..

(The same yaml config files work in 3.3.13 - I just changed ezpublish: to ibexa: at the highest level)