What is the default sleep time for spinning hard disks?

If there is no access to a spinning hard disk, does Manjaro put it into sleep mode by default, just like Windows does? It seems like the HDD keeps spinning for hours even if I have not accessed it, but I am not sure.

Also, Windows has a GUI for such HDD power settings. I have searched the web for a Linux equivalent, but the only thing I found was a command-line utility hdparm. Is that the only way?

it is; hdparm - ArchWiki

I tried it but says APM_level = not supported.

Found in “Disks” → 3-dot menu → Disk Settings. Apply Standby Timeout Settings was off by default, so I enabled it. I will see if that makes the drive to go to sleep after idling.

means power management was off for the drive

should work, make sure you dont set aggressive(should not increase the frequency of drive going into and coming out of sleep for a given uptime) power management settings, in which case it shortens drive life.