I now found that it is sufficient to restart the user service:
pkill -u 1000 vmtoolsd
/usr/lib/vmware-tools/sbin64/vmtoolsd -n vmusr &
This is faster and doesn't need root permissions.
Also I found that VMware KB: Enabling debug logging for VMware Tools within a guest operating system describes how to enable logging. I think often unity is disabled after the notebook has been in sleep state for a few hours. After resuming the log shows:
[May 25 10:26:01.454] [ debug] [vmusr] UnityTcloExit.
[May 25 10:26:01.454] [ debug] [vmusr] UnitySetInterlockMinimizeOperation: Do not interlock minimize operations through the host
[May 25 10:26:01.454] [ debug] [vmusr] UnityPlatformRestoreSystemSettings
[May 25 10:26:01.819] [ debug] [vmusr] Relevance for (23490E0) 0x28004b6/0/0x165 is 0 (window type 7)
[May 25 10:26:01.854] [ debug] [vmusr] Relevance for (2348FA0) 0x28004aa/0/0x165 is 0 (window type 7)
[May 25 10:26:01.854] [ debug] [vmusr] UnityX11RestoreSystemSettings: Restored taskbar visibility.
[May 25 10:26:01.856] [ debug] [vmusr] UserTime is guessed at 668653788
[May 25 10:26:02.688] [ debug] [vmusr] Removing window 0x25d4455 from tracker
[May 25 10:26:02.701] [ debug] [vmusr] Removing window 0x2400f46 from tracker
[May 25 10:26:02.706] [ debug] [vmusr] Leaving unity mode
[May 25 10:26:02.706] [ debug] [vmusr] Rpci: Sending request='unity.active '
[May 25 10:26:02.717] [ debug] [vmusr] Rpci: Sent request='unity.active ', reply='', len=0, status=1
[May 25 10:26:02.717] [ debug] [vmusr] UnityUpdateState: success