Description This article describes how to set up Multiple-PDN
WAN-Extension in VLAN mode with LAN interface. Scope FortiGate and
FortiExtender-511G/FortiExtender-511G-WiFi. Solution The scenario below
was tested with the following build and interface...
Hi based on your setup FortiExtender (LAN port) <-> Fortigate 60F WAN2
port. it's possible to achieve your goal, please refer
https://community.fortinet.com/t5/FortiExtender/Technical-Tip-How-to-setup-FortiExtender-WAN-Extension-CAPWAP/ta-p/215494