When changing the symbology of an annotation, the following warning pops up:
Why is it set so that features will continue to follow the old symbol? Wanting to change the symbol of all these features is precisely the reason I am changing to a new symbology! Why else would I change it if I want to keep the old symbology? It doesn't even make sense! Else I could just add a new annotation class with a new symbol!
This means I have to use the field calculator to recalculate the SymbolID field, which last time first caused ArcGIS Pro to crash, and then the leaders were missing.
I would prefer that the symbol I am changing gets to keep the original Symbol ID and AnnotationClassID, so that all the features automatically get the new symbol. That just makes so much more sense if you want to change the symbology of an annotation.
(This worked much better in ArcMap.)