I'm currently not aware of a command to consolidate snapshots for a single virtual disk. The GUI as well as the available commands work for a virtual machine.
Ways to merge snapshots into base disks are to manually clone a virtual disk using the vmkfstools command, which however requires additional disk space for the clone, or to create a temporary VM with just the virtual disk that you want to consolidate (Caution: This requires to edit the VM's configuration file, i.e. set the virtual disk name to the current snapshot!!! Otherwise it'll break the snapshot chain, which might case data loss, or corruption!).
Both mentioned options require downtime, and manual work from the command line. Not much work, but you need to know exactly what has to be done, and in which order.
André