In my rig we have no factory power in the slide at all. I had to install a long extension cord to go from under the dinette, around the back of the recliners, and hang loose near the slide lip so we can plug it in when the slide is deployed. We plug the other end into a power tower (
one example), so we can make it handy on the table when we need 120 and USB there, and tuck it underneath when we need the space for a meal. (In my last rig, I mounted a power strip on the wall underneath the table. Never again... it was like playing Blind Man's Buff to get anything plugged in.)
Extension cords come in a marvelous variety of lengths, so if you measure properly can you probably find a "perfect" premade one for your rig.
And yeah, we do plug and unplug it when we retract the slide. We got a low-profile sideways plug so we wouldn't have to, but we'd rather be chicken than strain something. In our last rig, we went through the effort to get a
"curly cord" so we could leave it plugged in, but the loops in the cord caught on the slide edge and threatened to rip the vinyl padding, so we gave up on the idea.