MAC and VM resource usage dynamic optimisation

Is there a way to allow parallels to dynamicly optimise my MAC resourses between the host OS and the VM's that I launch. If my host OS is idle and I have a Windows 10 VM running, it would be very handy if parallels could allocate more processors and RAM to to VM automatically. In the same way If I launch more than 1 VM, throttling back the resources on the open VM's to optimise overall performance would be great. Currently I have to do this manually. If I want to run a server and several clients, I have to manually configure less resources, then when I just want one open VM, say to use Visio, I have to configure more graphics memory and more RAM.