I recently discovered that the Card Browser visual does not allow changes to the "Metadata" fields when the report in question is connected to a separate Power BI dataset rather than a local model. This seems like an odd limitation of the card browser visual. To make a change to the metadata, I had to open two copies of my report, change one of them to Direct Query mode, modify the metadata then copy the visual back into the original report.
The "Metadata" you mentioned is to change its column name or the value ? As we all know ,that if you connect to Power BI Dataset ,the connnection mode is Live connection , that means you cannot change the value in Desktop directly . We usually change data in data source if the connection mode is Live connection . So, it's not really a problem, you can't modify the source data directly in Live connection mode . But you can shange column name in visual .