I've tried several hard tool boxes and found what works best for me is an open soft sided tool bag with lots of pockets and loops similar to this one:
https://www.harborfreight.com/19-in-...ets-61470.html
Lets me see and find what I need fairly easily and is easy to carry around.
I also have one (very similar tools/parts in fact) that I keep in my garage so I can grab it and head to fix most any problem at a relative or friends house. This happens WAY too often

I do keep one of those all in one mechanics tool kits in a carry case in the truck for emergency repairs away from home. JEGS has some really good ones in cases where the tools don't fall out when you open them

I just bought 4 of them and jumper cables for the kids/grandkids cars. They aren't the highest quality tools, but good enough for emergency repairs.
But I do agree, I haven't found any all in one kit that has everything you need for overall maintenance of an RV. So I built my own over the last 40 years
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Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder