We also have a 2018 Grand Design Reflection 337 and are right now traveling across the country (from TN to West Coast to East Coast and back home!) I feel like I have gotten a good handle on how to stow things for travel so I’ll try to list my methods and products. First I LOVE having a homey camper so I have LOTS of decorating items that I used to have to get out and put away every time we moved. No more!! I found out about using Museum Putty to stick things in place and it works like a charm for things like lamps and knick-knacks. Then there are Command Strips!! An RVer’s answer to just about anything else!! I use them to mount pictures, calendars, bathroom towel racks, key hanger, Reflectix insulation on bathroom skylight and front door window (anywhere the sun comes in too strong). It removes easily and usually does no damage at all, but does need to be replaced occasionally if you are hanging something unusually heavy (I use a heavy duty one to hang deer antlers!!! :)
I pick up my decorative round rug that is in front of the fireplace and put it on our bed and lay things across it that I don’t want to fall down (like my guitar, etc.) I make sure the closet doors are secured with the snap thingies, pull in the slide and close the bedroom door. I stow my bathroom lamp in the linen closet (removing the bulb and lampshade first so it doesn’t roll around and mess up the fixture), and I have a soft basket that I keep in the shower floor for the shampoo, soap and candles during travel. Make sure the shower door and bathroom door are secured (also that your toilet paper doesn’t fall and unroll during travel :-)
Everything else stays put very securely in the linen closet. Occasionally things will fall over in the medicine cabinet but nothing is damaged.
I have a basket with a flower arrangement, a tin with pine cones and a lamp on my dining room table. That all gets stowed under the table for travel as well as the Kleenex box. We used to secure the dining room chairs with the straps but no longer do that. Instead I cut some pool noodles to about 12” pieces and made a slit long ways to fit down over the sides of the back of the chairs to keep them
from bumping or rubbing on the wall or each other during travel. It’s worked great! The water purifier, dog food and water bowls, candles and butter bell stow in the sink for travel (I use a plastic sink protector to keep scratches to a minimum in the stainless steel sink). The coffee maker and toaster go under the sink along with my paper towels.
The TV has a great snap-in mount that keeps it secure during travel. I have only very rarely had any of the cabinet doors come open and usually only because I had something very heavy that fell against it, or an extremely bumpy road. I even have lots of glass dishes in the hutch cabinet (the one with glass doors) and have never had it open, nor has anything every chipped or broken. I do use a piece of that rubber cabinet liner on each shelf to keep things from scooting around and it has worked great!
As for the glass-fronted pantry, I use those spring-loaded rods that you can get in camping stores and put those across the 3 shelves. I also use OXO “air-tight” canisters to store most of my food items in (more for mouse protection than anything else, but they have squared sides and fit side-by-side and stack really well!) We mounted 4 spice racks on the inside of the pantry door and that probably helps to keep things in place as well.
I’d say that the cabinet I have the most trouble with is the one over the recliners. I store my books, maps, etc. there and they do shift around quite a bit. So I also put some fleece throws and neck rolls in there between the books and the door and that has worked better.
I have a small coffee table in front of the sofa and for that I place it upside down on a fleece blanket with the excess thrown over the legs to prevent it from sliding into the glass fireplace during travel. It fits nicely between the closed slides and has never moved during travel.
I have a check-off list that I printed out with a label maker and stuck inside the indoor control panel and use that every time I get ready to move to the next campsite. It has saved our bacon a few times!! I don’t have a picture of it, but I can post it once we get to our next destination. I’m sure you’re going to LOVE your new fifth wheel and it’ll become second nature to you once you’ve done it enough times!