UMG—— Re-Open the project and the user created content is missing.

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I inserted “Weapon” widget into “GameHud” by the user created content. It’s work.
But when I re-open the project, “weapon” widget is missing. It’s still in the “GameHud”, but I can’t see it.
However my “Inventory” widget is still work.
What can I do? Thanks for your help.:slight_smile: