Hello @krisnov , Thank you for reaching out.
Apologies for the delay. You can follow this GitHub comment here to pass key vault secrets as parameters in ARM template in your sftp connection. You can refer to this documentation regarding the template used. If it helps here is another way for adding Multi Line secret value to your Key Vault.
Here is the documentation for how to pass key vault reference in the parameters file.
Please let me know if there are any additional concerns, I will be glad to continue with our discussion. Thank you!