A request XML packet stopping the migration includes the finish operation node:
<packet version="1.4.2.0">
<migration>
<finish>
¡
</finish>
</migration>
</packet>
The finish node is presented by complex type MigrationId (plesk_migration.xsd), and its graphical representation is as follows:

With one finish operation, you can stop only a single migration. To stop multiple migrations with one packet, use the required number of the finish nodes in your request packet.
In case of Plesk for Windows, with the finish operation you stop the current migration.
This packet stops the current migration performed by Plesk for Windows Migration Manager.
<packet version="1.5.2.0">
<migration>
<finish>
<migration_id>1</migration_id>
</finish>
</migration>
</packet>
This packet stops the migration with ID /opt/psa/tmp/supervisor.24174.
<packet version="1.5.2.0">
<migration>
<finish>
<migration_id>/opt/psa/tmp/supervisor.24174</migration_id>
</finish>
</migration>
</packet>
This packet stops migrations with ID /opt/psa/tmp/supervisor.24175 and /opt/psa/tmp/supervisor.24176.
<packet version="1.5.2.0">
<migration>
<finish>
<migration_id>/opt/psa/tmp/supervisor.24175</migration_id>
</finish>
<finish>
<migration_id>/opt/psa/tmp/supervisor.24176</migration_id>
</finish>
</migration>
</packet>