How can I specify for an existing VM (in VMWare Player) that the UEFI Secure Boot Mode is enabled resp. disabled?
I guess there is a corresponding variable in *.vmx file
Which excatly?
In Workstation Pro there's a checkbox in VM Settings → Options tab → Advanced to enable secure boot; if Player doesn't have that, try adding uefi.secureBoot.enabled = "TRUE" to the .vmx file.