Unfortunately binding a collection of annotations is not possible at this point, but you can try the approach described in this thread
. As mentioned there, we have an item in our Feedback and Ideas portal
about this feature and you can upvote it and subscribe to it in order to receive any updates on the matter.
Regarding your second question, it is possible to place the annotations behind the chart series through the z-index, but the z-index of the annotation needs to be significantly smaller. If you set it to "-200" for example, you should be able to achieve the desired result.
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Do you want to know when a feature you care about is added or when a bug fixed?
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and vote to affect the priority of the items