in a multi master (3 masters) Kudu installation deployed by Cloudera Manager (parcels CDH, version 5.13) is it possible to migrate one of the masters into a newly added host in CM? Is there any Cloudera documentation how to move a master role?
It's possible, but I don't think there's a guide for this exact procedure. Here's one approach that directly moves the contents of one machine to another, assuming you want to move from "masterA,masterB,masterC" to "masterA,masterB,masterD":
Shut down the Kudu cluster.
Copy the contents of masterC's `--fs_wal_dir` and `--fs_data_dirs` directories (the `--fs_metadata_dir` configuration doesn't exist in 5.13) to the corresponding directories in masterD, using your favorite remote-copy tool of choice (scp, rsync, sending over a USB stick, etc.).
From there, you should be able to follow the "Changing the master hostnames" docs you pointed to. Since you're using CM, you can ignore the steps that specify changing the gflagfile.
Add masterD as a Kudu master and remove masterC as a Kudu master in CM.
Restart the Kudu cluster and verify the cluster can come back healthily.
For safety, remove the contents of the `--fs_wal_dir` and `--fs_data_dirs` directories on masterC, ensuring it can never come back.
Also if you're using Impala, you'll want to invalidate metadata to pick up the new masters.