I created a data asset with content and placed it into a blueprint variable. When I reopened the project, all the content of this data asset was gone.

[zhao0709]

I created a data asset with content and placed it in a blueprint variable.
After closing the project and reopening it, all the content in the data asset was cleared.

[zhao0709]

These are the settings before closing the project.

[zhao0709]

I only referenced it in the blueprint.