I gather up loose items like you mentioned and put them in a bin. I store the bin on the floor of the trailer somewhere where it won't get in the way of a slide-out while putting the slide-outs in.
You can also store a few items in the sink during transit. My bottle of hand soap and the stove kettle go in the sink.
If you have stuff in cabinets, you have to keep in mind that sometimes the doors will open and stuff will jump out in transit. I use a bungee cord to keep some doors closed. Also maybe it's a good idea not to store something really breakable in a cabinet that is high up and the item is placed close to the door. If the door opens in transit it's best if non-breakables fall out instead of breakables.
I store a lot of items in cabinets in bins. The reality of RVing is often you have to sort through a lot of stuff to get what you want. If the items are sorted and stored in bins, it's easier to locate things. For example, a lot of my small kitchen items are in one bin, small food storage containers in another, stationery supplies in another, etc. You can find bins of almost any size in stores these days. Things also like to move around in the cabinets so bins keep the stuff together. Things like plates and bowls are just on the shelves in the cabinets.
I put a bunch of pantry items (oil, vinegar, bread crumbs, etc.) in a basket. I just haul the basket out when I need something. If I just placed these items in the cabinet, they would be everywhere after transit.
You can also buy sticky pads to keep things in place. They stick to the item and to the counter and can be washed and used again. I use one to keep a container of spatulas, etc. on the counter. It stays there even during transit.
2017 High Country 305RL
2015 Ford F-250 Super Duty