Prerequisites
The order type or project profile have to be created already in Customizing for Investment Management:
Define Model Orders.
Define Project Profile.For it to be possible to generate maintenance orders from appropriation requests, a PM order type has to be defined as relevant for investment measures. You make this setting in Customizing for Plant Maintenance and Customer Service. Choose Maintenance and Service Processing ®
Maintenance and Service Orders ® Functions and Settings for Order Types ®
Order Types and Investment Management ®
Indicate Order Types for Investment Measures .
Procedure

When you create WBS elements, you also have to create a project definition for them.
Result
When you save, the system creates the measure(s).