MACHIN3 (MACHIN3Tools dev) was kind enough to solve the 2.93.0 woes for Set Dimensions:
Replace
new_x = FloatProperty(name="X", min=0, default=1, unit='LENGTH')
new_y = FloatProperty(name="Y", min=0, default=1, unit='LENGTH')
new_z = FloatProperty(name="Z", min=0, default=1, unit='LENGTH')
with
new_x: FloatProperty(name="X", min=0, default=1, unit='LENGTH')
new_y: FloatProperty(name="Y", min=0, default=1, unit='LENGTH')
new_z: FloatProperty(name="Z", min=0, default=1, unit='LENGTH')