Can't copy/paste transform variable default values in the details panel

We can't copy/paste on default values of transform variables in the details panel.  Other variable types work as expected and transform types can have copy/paste applied like this in other blueprint editors. 
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1. Create a control rig
2. Create a transform bp variable
3. Compile the control rig and select the variable
4. R-click on the variable's default value in the details panel
   1. Expected behaviour: Copy/Paste can be selected
   2. Actual behaviour: Copy/Paste are disabled