When uploading historical csv data, I failed to assign the data to my existing bank account, and there appears no way to change the Account label from its current status of Imported File - Manual Upload.
The only way I can see to do this so far is to tag and delete all affected transactions, and re-upload the file after ensuring the correct account assignment during the upload process. This is not ideal, as I have already categorized many of the transactions prior to discovering this problem, and all of that work would be lost if I was to delete and start over.