Currently, there is no way for a user to set the order of their Data Properties.
There are additionally instances where the order of Data Properties in the Data Structure doesn't match the order in its Data Set, without any method to fix it.

Repro Steps:

1) Create a Page with a MainPage.xaml
2) Create a DataStructure containing 4 Data Structure Properties. (leave as the default Type, default Single, and default names Property0000, etc...)
3) Create a Data Set from the DataStructure Created (no need to fill out values).

4) Toggle back and forth between the Data Structure, and the Data Set.
Observe how the order of the Properties in each match up.

5) In the Data Structure, delete the two first Properties Property0000 and Property0001.

6) Toggle back and forth between the Data Structure, and the Data Set.
Observe how the order of the Properties in each match up.

7) In the DataStructure, add two more Data Properties with their default values.

8) Toggle back and forth between the Data Structure, and the Data Set.
Observe how the order of the Properties the Data Structure, and the Data Set do not match up.

Expected Result: The ordering of Data Properties matches up between the Data Structure and the Data Set.
Expected Result: Data Properties in the Data Structure can be manually re-ordered with a dragger, and any changes in the re-ordering in the Data Structure is mirrored in the Data Set.