You can find this window by selecting one more more loans in the main list of loans and clicking Tools > Export Selected Loans to a Different Portfolio.
Click Browse to select a location and set the new file name or choose an existing portfolio file.
Copied loans should overwrite/update the destination. - When checked, the copied loans will keep the same ID values as the source portfolio. If these same loans are copied again to the destination, the records will be updated with the values from the source. Note that records which have been deleted in the source are not automatically deleted in the destination. If this box is unchecked, the loans and associated records are assigned new internal IDs when copied, creating loans that are entirely distinct from the loans in the source portfolio.
Click Export to copy the selected loans to the destination portfolio.