What it does
I'm not familiar with "Stowage" as an official Magic: The Gathering keyword or ability. It doesn't appear in any official rules text or card set that I'm aware of, so I can't accurately explain what it does, its rules nuances, or how it matters in Commander.
It's possible this is a custom/homebrew mechanic, a misremembered keyword name, or something specific to a particular community or set I don't have information on. You might be thinking of a similar-sounding ability—for example, "Storage" counters (older cards like Storage Matrix or storage lands), or perhaps a mechanic from a fan set.
If you can share where you encountered "Stowage" or the text of a card that uses it, I'd be glad to help interpret how it works and its Commander implications.
Iconic cards with Stowage
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