I found the way how to make multiple snapshots on VMware Server.
After creating first snapshot the vmsd and vmsn files are created as well as disks snapshots.
To make second snapshot (from the previous one) it is necessary to change name of the snapshot in vmsd file :
snapshot#.displayName = "VMware Server Undopoint".
Then you can create next snapshot. Of course the second snapshot name will also be as above and has to be changed manually in vmsd.
If you want to revert to any of the snapshot you have to do it manually - change disk names in vmx file and remove snapshotX entries from vmsd file and correct global in vmsd (number of snapshots, current snapshot) and delete corresponding vmsn file.
Maybe someone from the Forum could do simple SnapshotManager to handle this simply (with GUI)
BTW: VixVM_CreateSnapshot ignore name and description parameters. Maybe one of VixSnapshot_... function could do this as well as create or revert multilevels snapshots.