How to add a new operating unit type

For AX2012, you can follow the steps in this link https://msdn.microsoft.com/en-us/library/gg989762.aspx
Couple of important points:

1. The new enum value must use the immediate next number for that enum (you should not skip any number)
2. The new enum name drives the view name that you need to create. AX will look for a view with "DimAttribute" prefix after the enumeration name.
   For example, if the new enum name is OMBranch then the view name must be DimAttributeOMBranch.

For D365, it is quite similar to the steps in AX2012, however in the view it should have a method called registerDimensionEnabledTypeIdentifier and you should use the view name that you just created. This will then add the new operating unit as a dimension type.

Keep in mind that in D365, there are 3 additional operating unit types (branch, rental location, region) that are part of the Fleet Management model, which is actually a sample model and doesn't get installed by default to tier 2 or production environments.