Hi,
if you are using routing on the edge switches, you can create a virtual router the same way as on the core switch. According to the
Feature License Requirements document that is supported on about any recent layer 3 EXOS based switch.
If the edge switches are layer 2 only, you just need to add the VLAN. The virtual router pertains to layer 3 only.
To add VLANs from different virtual routers to a trunk link (this would be on the X8 side for layer 2 edge switches or on both sides between X8 and layer 3 edge switch) you need to remove the port from VR-Default. If a port is associated with a specific VR, only VLANs of that VR can use the port. If a port is not associated with a specific VR, any VLAN can be added to that port.
Thanks,
Erik