XS_VALID_CHARS_FOR_ASSEMBLY_MULTI_NUMBERS
Category in Advanced options dialog: Numbering
Use to specify the valid letters for assembly multinumbers. You must specify all the valid letters in this advanced option. By default, letters A - Z are valid.
This advanced option is model specific and the setting is saved in the options database.
Example
XS_VALID_CHARS_FOR_ASSEMBLY_MULTI_NUMBERS=ABEG