Moving Comcast router
 

I have two boxes for my TVs. One primary (adjacent to the router) and a secondary in the LR. I want to move my router to a more central location in the house to improve my wifi connection on the lanai. Is it just a matter of unplugging and replugging it into the LR cable wall outlet? Do I have to move the boxes? I don't want to open Pandora's box.

Yes, you should be able to move the router to another cable outlet. Are the cable boxes wireless? If so, as long as you don't move the router too far away, you should still get a good wifi signal. If the cable boxes are wired and connected to a cable outlet, then they don't even need the router to deliver cable TV channels. Xfinity (Comcast) cable channels and some apps are delivered through the cable, even if you don't have internet service.

Make sure the cable wall outlet you want to plug into is actually active. Most of mine are not - they are wired to the low-voltage box but are not connected within the box.

Just make sure that the outlet you want to connect it to is actually live. When they came out to hook up our cable and internet they only hooked up the wires to the connectors we needed. You might just have a bunch of unterminated cables in your low voltage box. In that case you will need to identify the cable going to the outlet you want to use and install a connector on it

I dropped a cable outlet in the back wall above the cabinet above the refrigerator. There is already an AC outlet. Installed modem and router on top of cabinet (hidden with artificial plant). The height and central location of the router allowed for excellent coverage of the whole house and the lanai.

Correct ... and the more ports you activate (connect to splitters) the more loss you get in your CABLE TV and INTERNET service . Each additional port activated adds about 3DB to 5DB of loss depending on splitter quality, which (not counting cable and connectors which create loss as well) enough to make a difference. Exceeding 3 active ports could introduce TV issues on many channels, as well as internet issues. My loss doubled when I went from 2 to 3 ports active and when I added a 4th active port I had to add a amplifier so I used another method. My cable modem has a signal monitor and it's quite interesting to watch how every device and even coax quality affects signal. Adds up fast. I am sure new construction areas take this under consideration but down here the infrastructure is 14+ years old. There was a 4-way splitter (2 ports used) and I replaced it with a 2-way signal doubled.

Couldn't the OP just remove the old cable from the splitter and connect the new one to it?

Absolutely, unless the old cable was also being used on his TV which is what it sounded like since he said he had 2 TV boxes. There had to be a splitter there as well (into the splitter out to the TV & modem) which isn't quite as bad as the splitter at the dmarc which affect the entire house. Also, hopefully he has no ethernet connections at the router when/if he moves it or he would have to rewire those as well.

I ended up switching over and using a mesh system check it out you'll be much happier I tried the router all over the house in every different room and could never get Wi-Fi out of my line and in the back bedroom

just move the router

You have an rg6 cable going to your modem/router box which is terminated in the network box. You will have to change this cable in the network box to the cable in your lr. Doing this MIGHT improve your wifi because the router you get from xfinity/spectrum are not that good.
I actually left my internet vendors modem/router in a back bedroom and did the following:
1: I terminated all cat6 cables in my network box and reterminated all phone jacks to rg45 and put rg45 terminations on all cat6 cables.
2: I bought a new wifi 6e mesh network pair of routers and put 1 router above the kitchen cabinets (central location) and configured it in wired bridged mode and put the 2nd mesh router in the lanai in wireless bridged mode.
3: a lot of people don’t realize that most wifi products in your home operate at the slower speed 2.4ghz band. So what I do is put a router near my media/tv areas where I have a tv/Apple TV/dvd/PlayStation/or another networked device and hook up all of these devices to the router or to a switch and then hook the switch up to the router so now all of those devices are using a wired connection.
4: my wifi speeds over the whole house has increased f I’m the middle 300’s Mbps to almost 800Mbps.

I just finished playing the "move the router/reset the router" game on my top quality router. I got fed up and bought a two unit google Nest Wifi mesh system. It was the easiest thing to set up and holy smokes, my speeds are now exactly what I am supposed to be getting! I did have a question while setting up, and contacted Google. They answered the phone in 1 minute, answered my question, and then stayed on the phone while I finished setting up and tested everything. My two pack was $109 on Amazon. The second access point device is also a Google assistant/speaker, the "hey Google, could you play some 70's music, set a timer, check the weather, ask questions...kind" but you can turn off the microphone on it so it can't operate in that manner if you don't want that. It's the best change I've made!

That’s not true about the more devices you hook up the slower your system becomes. I have had 5 TV’s all hooked up to rg6 using Dish’s splitters with no degradation in picture quality. As for network, you can have hundreds of devices in your home and if you do it right, you won’t see any degradation.
But, saying this, you have to plan your internet speeds wisely. If you have 5 people streaming or downloading movies/files on a computer all at the same time, you won’t want to get a 10Mb internet connection just like you wouldn’t get a Toyota Camry to pull a 10,000 boat. I have a 1200Mb internet for 2 people and I don’t wait for streaming movies to buffer.
As for networks, you get the appropriate number of routers (preferably mesh) and switches for your needs

old yeller, call Xfinity/Comcast and cry a few tears about the wifi coverage in your house. Tell them you heard about a Booster. You get one for free when you have a coverage problem. Just plug it into an electrical outlet on the other side of the house and you will be fixed up within moments. Impossible to goof up. No programming or wires to deal with.

No, “replugging” won’t work, but the solution is almost as easy. Just run Ethernet cable up inside the wall from the original entry point, probably on an exterior wall, up to the attic, across to a more central wall, then down where you’d install a new Ethernet plug and plate. Then plug your router in that more central location. I had it done by a handyman. The cost of the cable and plate were more than the handyman’s labor.

Why or why didn’t I have this done years sooner? I also had a mesh system installed and from the new centrally-located router that really extended wi-fi speeds thruout the house, even out to the pool deck!