Adding an element to an array in the Material Editor automatically collapses all expanded elements in the array.
I've successfully reproduced this issue with the following nodes:
I'm able to reproduce this issue as far back as the live 4.20.3 Binary (CL 4377374). I cannot reproduce in the live 4.19.2 Binary (CL 4033788).
It is therefore marked as a regression.
The Grass Types array collapses all elements when a new element is addd
Expanded elements are not collapsed when a new element is added
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-72258 in the post.