This article describes that VLAN interfaces configured with large number of references take a lot of time to migrate from one interface to another as every reference have to be moved one by one individually.
Interface migration wizard got introduced from FortiOS 7.0 which helps in migrating the References from a physical Interface to either an Aggregate interfaces, redundant interfaces or software switch.
However for VLAN interfaces this option is greyed out and this article shares a solution to migrate the VLAN interfaces along with referneces from the Parent Interface to FortiLink interface.
FortiGate is Configured with 3 VLANs (Vlan60, Vlan80, and Vlan100), and all VLANs are configured under interface port17. All VLANs have some references used for Policies, Address Objects, Static routes, or VIP.
Take a config backup of the FortiGate before migrating the interfaces and have the changes scheduled in a Maintenance window. Avoid accessing the FortiGate with the same interface to avoid being locked out).
For Individual VLAN Interfaces, the Option to Integrate the Interface is Greyed out.
Then Select Migrate to Interface and select 'Next'.
The next step involves selecting the Target interface and for this example, FortiLink is selected and select 'Next'.
Entries are Successfully updated, So it is time to Close the Wizard and verify the migrated objects.