I'm trying to configure the amount of RAM dedicated to my current Win10 VM, but when I click on the configuration (gear icon on to right of VM screen) Parallels stops responding.
this seems to be a known issue at the moment. I suggest that you edit the config file with your favourite text editor. It is just a simple XML file located inside of your virtual machine folder. Find your VM, right click and choose show contents. Edit config.pvs file. About half way down you will see the section for RAM. I have minne set to 6Gb <RAM>6100</RAM>