hey @S Reiner, glad to hear you're using Doodle! and thanks for the feedback. it's great to hear that the features are helping with actual projects.
you have actually found a real bug; so thanks for reporting it. the issue is that zOrder is done using z-index in the browser, and there are some bugs like this it seems. i reproduced the issue and will be working on a a fix for 0.9.2.
in terms of draw order, items are drawn in a sort order that uses zOrder first (higher being drawn later) and then index in the container.