To expand on the above discussion, in the latest wip, the User Text now works prior to baking as expected. But I tested to assign the User Text on transformed block definitions or existing block instances, and the user text fixed to block attribute could not be modified by bake/update, and also it could not be previewed with a new-assigned attribute.
@AndyPayne Sorry for the late reply, I have tested the latest beta version, and it seems not updated for this, and I also found another issue. Please see below:
#1 it seems to get wrong when display in gh that will always display the last created block attritbutes.
#2 blockinstance in gh will not display the modified attributes #3 Attributes of baked blockinstance will unexpectedly reset to default value. #4 baked block instance will out of tracking by the bake component, can be repeated with the second cllick and it turned yellow for warning.