There seems to be only one global setting for the pre-shared key for all VPNs of an instance (or company VPN group of instances). This setting should be within the VPN setting and not a global setting outside. The PSK is shown in the settings of each VPN, but it cannot be edited and is identical to the global value. It also changes when you change the global setting, so it is not only a usability issue of the gui.
Thank you for your great idea. While we cannot commit to a specific target version, we will consider adding it to our future internal backlog. If you can add further information about the context of this feature, please add it here so we can evaluate it more fully.