For OptionSets based on numeric DataTypes it is not allowed to add new Bits (see 3.2.7). Therefore, either a new DataType is created having the old and new bits (with all the implications), or a new DataType is created just having the additional bits and the usage of that new OptionSet is added, wherever the old one is used.

For OptionSets based on the OptionSet DataType, it is also not allowed to add new Bits (see 3.2.8). However, subtypes can be created supporting additional Bits, as long as the overall length is not changed. As alternative, the same approach as for numeric OptionSets apply.