✨ EDITABLE_STEPS_PER_UNIT (#26618)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/inc/SanityCheck.h

@@ -458,6 +458,8 @@ static_assert(COUNT(arm) == LOGICAL_AXES, "AXIS_RELATIVE_MODES must contain " _L
 #if ENABLED(I2C_POSITION_ENCODERS)
   #if !ALL(BABYSTEPPING, BABYSTEP_XY)
     #error "I2C_POSITION_ENCODERS requires BABYSTEPPING and BABYSTEP_XY."
+  #elif DISABLED(EDITABLE_STEPS_PER_UNIT)
+    #error "EDITABLE_STEPS_PER_UNIT is required for I2C_POSITION_ENCODERS."
   #elif !WITHIN(I2CPE_ENCODER_CNT, 1, 5)
     #error "I2CPE_ENCODER_CNT must be between 1 and 5."
   #endif