Place:

readable_test_background.dds -> <FMname>/dds/guis/assets/readables/sheets/
sheet_test.gui -> <FMname>/guis/readables/

1. Create a single-page readable entity.
2. Select it and bring up the Readable Editor.
3. Use the gui browse button to bring up a list of available guis.
4. Note that "sheet_test" isn't present.

Place

test_entry.xd -> <FMname>/xdata/

5. Restart DR.
6. Select the readable entity from above.
7. Bring up the Readable Editor.
8. Use the XData Name browser button to bring up a list of available definitions.
9. Select "blue_white_letter" (defined in test_entry.xd).
10. The RE now correctly shows guis/readables/sheet_test.gui as the Gui Definition.



So, to get DR to recognize a custom gui, you have to start with a manually-created definition that references it.