S/4HANA FLP WebDynpro APP directly go to URL of backend server

Hi experts,

The My Account Bank Worklist Web Dynpro App is configured according to Fiori app reference library (LPD_CUST has been configuration to use HTTPS connection to the backend).

We use HTTPS connection to the backend server (central hub environment, S/4HANA OP1511 FPS 02). Whenever clicking this APP in FLP, I see an emtpy screen. In web consule of Google Chrome, the following error is shown:
https://backend_server_hostname:backend_HTTPS_port/url
Failed to load resouce: net: ERR_INSECURE_RESPONSE

I can open this backend url with new tab and adding exception for certicate in Google Chrome.

However, we only want to public web dispatcher hostname and its HTTPS port to end users not backend server related hostname and port, how to fix this issue?

Regards,

Ning