Just quick test with Calibre 7.7 (released 2024-03-14):
source epub (positions of soft hyphens signalized as "{sh}"):
Code:
Aaa{sh}aaa aaa{sh} aaa {sh} aaa {sh}aaa.
docx conversion output (Calibre 6.26, Calibre 7.7):
Calibre version 7.7 preserves spaces around soft hyphens. As expected.
Thank you.