If you want a custom filter to have there only virtual machines, then you can manually create a custom Filter in "Raw SQL" query mode using this SQL Query
- This Query shows only managed Virtual machines (without physical computers)
SELECT [Guid], IsManaged
FROM vComputerResource
WHERE IsManaged = 1 AND ResourceTypeGuid = '2C3CB3BB-FEE9-48DF-804F-90856198B600'
- This Query shows only managed physical machines (without virtual machines)
SELECT [Guid], IsManaged
FROM vComputerResource
WHERE IsManaged = 1 AND ResourceTypeGuid = '493435F7-3B17-4C4C-B07F-C23E7AB7781F'