Thank you @bojanvelevski , perfect it is working as expected.
Thank you @kkishore, can you please mark @bojanvelevski’s suggestion as a Solution so that anybody looking at this thread in the future can refer to the solution directly?
Assuming your input is a single document with an array of objects, rather than a stream of individual documents.
With that assumption you can use a mapper with the expression:
jsonPath($, "$[*].tree") and target path: tree
This will collect all tree objects from every element in the array, then write that list to the target path tree
