Manual transfer switch for connecting gennie?

You need a double pole, double throw switch, preferably center off so that you're sure the switch is break before make (though most are). The switch should be rated for 120V 30A minimum, and preferably a little higher. Both the hot and neutral get switched, the safety ground is solid through.

Any switch suitable for 30A 120V service should be capable of having 10 gauge wire connected, albeit possibly using a quick connector or something.

(The hot and neutral both get switched because, if the generator bonds neutral to ground, failing to switch the neutral creates a ground fault in the RV when connected to shore power. Per the NEC a permanently connected built-in RV generator should bond ground and neutral. Most portable generators do not, but it's possible that some can, and you could in theory connect the generator connection to something other than a generator that does.)

A safe and easy and inexpensive way of hooking this up is to simply install a 30A RV socket in your RV's cord storage compartment and wire that to the connection to the generator. When you aren't plugged into shore power, plug the shore power cable into that socket and you're connected to the generator. It's pretty well foolproof, and obviously it's impossible to connect both the generator and shore power at the same time so it's perfectly safe. Frankly, this is the approach I'd recommend, though it is arguably slightly less convenient to use.

Probably easier to get an automatic switch. Or just plug the main cord into the gen right after you pull start it.

You need something like this :
Rotory cam switch

What DrewE said.

It’s what I do. And yes, if you do a swith, double pole double throw, being careful to wire it so that the shore power and generator lines are the ones being switched between, with the load, ie trailer, being the line that moves one to the other. And center-off is a very good idea.

Regrettably the TT cord storage compartment is not accessable. Shore cord just pulls from the outside. That's why I'm leaning towards the switch. I'll have to pull the WFCO power center just to get in and wire a switch.

Would this switch work?
***Link Removed***

Sounds like as long as I switch the neutral as well as the hot I don't have to worry about bonding neutral to ground?
I think I prefer a rotary switch however many of them say they are three pole. I can't see how that works when these switches only have three positions on The rocker arm. Shore, off and generator.
Thanks again.

Generally, you wouldn't need to bond neutral to ground at the generator. If you have an EMS, it might complain (and not let power through) unless you do, but it's not an electrical requirement for any appliances or devices, nor is it a particular safety hazard with a portable generator to leave the output entirely floating.

A three pole switch means it can switch three wires. A three pole, two throw switch with an off position would have three physical positions for the knob or lever: on, off, and on. A three throw switch has three on positions (and might have one or more off positions as well). You could use either a three (or more) pole switch, or a three (or more) throw switch, and simply ignore the extra contacts. Three pole switches are somewhat common because they're often what is required for various things that use three phase power.

Just install this relay and parallel the coil with the generator input.
https://smile.amazon.com/gp/product/B07FCJFGL9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Hook the power center to the operating points, the shore cord to the normally closed and the generator input to the normally open.
Switches both the hot and neutral. Wire the grounds all together.

Easy and passive so you cannot forget.

Housted

Did something similar.....
https://forums.trailerlife.com/index.cfm/fuseaction/thread/tid/29746971.cfm