Hi @Joel Soutenare -
Location is an dimension specific to Labor. As a result, it is only selectable (showable) in the Labor and financial (Opex and Capex) line item views so that you can group/filter labor related financial amounts by Location. It is analogous to Asset and Contract only attributes like Asset Class and Contract Type.
One potential way to workaround this is to add a Location attribute to the Cost Center dimension using the Edit Columns function (see What's New in November 18, 2015 Release for an example of this). In this way, you can select the location by selecting the Cost Center. This of course only works if location choice is directly related to the cost center - which may or may not be the case with how you wish to use location in the context of a contract line item.
Of course, you could always create a 2nd Location dimension (Contract Location) and simply upload the same values you used for Location. This has the drawback that you need to remember to update both dimensions should your Locations change.