How to update source string in string table programatically

I don’t have the editor in front of me at the moment to check but this smells of an asset registry issue. Have you added the string table/path to your asset manager?

Here’s an old post on the subject. It’s not exactly your problem as it’s in BP but it might give you some leads.

String Tables not loaded at start - Programming & Scripting / Blueprint - Epic Developer Community Forums (unrealengine.com)