Hi @LilacOTR,
So I'm assuming you created all of your items in Square Online (rather than Square's main Item Library:Square Dashboard (squareup.com))?
If that's the case, I hate to be the bearer of bad news but customer service is right (as far as I understand how Square's systems work / talk to each other). Square Online doesn't seem to talk back to Square's main systems apart from inventory etc once imported from the main Square system.
It seems items need to be setup first in Square's main Item Library itself (not Square Online, which is an offshoot of their main platforms). Then once in there, you 'Add Items from Library' into your Square Online site, which then talks to each other with stock levels etc.
Are you using Square in a retail store as well, or are you only selling online? If you're only selling online, you may not need to worry about them being in the main Item Library. However if you're using in store too, unfortunately you might need to go backwards.
A key tip (after also learning things like this in the past the hard way) — maintain your own spreadsheet of items, this makes moving between platforms much easier (often you can copy and paste massive amounts of the content into the new platforms Excel / csv template and mass import. We've always been with Square for POS, but use Squarespace for our website / ecom (and also had to use Shopify buttons at one point (to support Afterpay)) — and now finally I've moved everything to Square Online for ecom but still use Squarespace for our website, but hoping to move this soon too. But the best part is no longer having to juggle our inventory across multiple platforms (so I feel your pain having to do this again!).
Square's Item Library does support importing though (available under the 'Actions' button > 'Import Library'), so I would highly recommend you start with just setting up all your items into their Excel template first, and saving it so you have it for next time. It's painful, but at least you've got it on file if you need to move later.
