Blueprint Structure tooltip edits get discarded. Current workaround is to make a secondary change that is not needed along with the desired change, Then edit it again to remove the secondary change.
Found in 4.18 CL# 3832480, 4.19 CL# 4033788, 4.20 CL# 4302132, 4.21 CL# 4359072
The tooltip will revert the changes made to it
Changes to the tooltip will remain
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-64019 in the post.