Click on VM > Backups > (drop down box) select which backup node or (random) by default.

Backups > Backup Nodes > (Exclude a backup node from (random) selection)

This comes in handy when you have multiple backup nodes for example SSD vs. NVME vs. Spinning or different teir levels for customers backups.

or... you just want to dedicated an entire node for your VMs vs. customers.