You would switch to the one that you need at the time.
To avoid configuration switching, two WiFi to Ethernet adapters, one set to dock WiFi and the other set to your hotspot. Then plug that into some router configured as a WAP if plugging these adapters into the WAN port doesn't work out.
I decline to write a step by step because the person who sets this up must be able to maintain it. If setup is required all network techs I know of can do this.
I want to manage how I receive internet - from public Wi-Fi or from Verizon hotspot. I have a boat that has numerous Wi-Fi devices that are connected wirelessly to an Apple AirPort Extreme. Currently I have a verizon hotspot connect wired to it for internet access. I would like to be able take the existing internet Wi-Fi at the dock and plug it into the Apple AirPort Extreme. To keep from using Data up on Verizon. By doing so I would not have to reconfigure connections each time I leave the dock. Thank you for the help.

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