Could you please confirm that the image that you attached to your original post shows only 3 annotations and that the annotation starting on the 25th actually has a duration of 5 days? This would be strange and unexpected as the alternating colors are partially transparent as you can see in the images in the help topic you mentioned
The default ZIndex of a timeline annotation instance is 300. That is, by default, a timeline annotation appears on top of the timeline items (default ZIndex=200) and the period items (default ZIndex=100). In case you want the third annotation to show as the first two in your image, you should use a ZIndex in the range [101; 199].
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