Repro Steps:

0) Create a new Studio Project
1) Create a Page
2) Introduce a Button to the root Grid.
3) Right-Click on the Button, and navigate to 'Templates', 'Button', then 'Create'.
4) Give the Template a name, and select to store it within GlobalResources.xaml. This will open the Template in the Template Dummy Editor.
5) Make any visual change to the Button which will differentiate it from the default style.
6) Exit the Dummy Editor, and Navigate to the Assets Panel (Ctrl+1).

7) In the Assets Panel's Folder Browser, create a new folder within the Project Root by hovering over the root folder, click the (+), and give it a unique name when created.
8) Find the GlobalResources.xaml file, and click-and-drag it to the folder created in Step 7).

Observe how the Button on-Stage, continues to be correctly displayed.

9) Close the application, and open the Project again.

Observe how the Button on-Stage, no longer displays the correct Template.

10) Right-click on the Button, navigate to the 'Templates' section, and then hover over 'Button',

Observe how the 'Apply Resource' option is disabled.

Expected Results:
Either moving GlobalResources is permitted, and retains links to its used Resources, or, moving GlobalResources is not permitted to prevent users breaking their projects.