8 Channel Relay use one GPIO as a switch input

I just bought one of these 8 Channel relay boards.ESP-12F 5V/7-28V 8 Channel Relay Board (ESP12F_Relay_X8) Configuration for Tasmota
I flashed it with tasmota and it works perfectly.

Now I am wondering if there is a possibility to use one of the ununsed GPIOs to create a switch input.

Can anyone show me the pins I would have to use and how to configure Tasmota for that?

Thank you very much for your Help.