Step-By-Step:

Below are the steps to import a subsite into another (or the same) Multisite network.

1. On the source Multisite go to Duplicator Pro > Packages > Create New: build a package (archive/installer)
2. On the destination Multisite go to Duplicator Pro > Import: Add the source Multisite archive.zip/daf file
   1. After the archive file is uploaded, click the Launch Installer button
   2. On Step 2 of the import add or copy the recover point (optional) and click the Continue button
      Note: Recovery points are optional but are recommended in the event the install runs into issues.
3. On Import-Installer Step 1 choose Install subsites on Multisite network radio button
   1. Choose the Subsite drop-down with the Multisite subsite you would like to import.
   2. Choose the Action drop-down with the action to add as new or replace existing subsite.
   3. Repeat above two steps for remaining subsites you wish to import.
   4. Click the Validate button and check the results then click Next button and let the installer run.
   5. When the installer is complete, Step 2 show a status of the install.
      If a recovery point was set then then both an “Admin Login” and “Run Recovery” button will show.
   6. Click the Admin Login to the newly created site and validate the install process.

When complete, you will have a new subsite installed or replaced in your Multisite based on the action chosen above.