I created some custom fields for items.
Is it possible to import them with the items to be imported?
I don't believe the standard LS Retail inventory import allows for this. Although there are third party solutions --> https://hyperspace.zendesk.com/hc/en-us/articles/360024461213-Importing-custom-fields-for-products-into-Lightspeed. And if you have technical staff available, it's definitely possible via the API.
One caveat I will offer. If you have a few thousand products and you are planning on implementing a fair amount of custom fields (e.g. - more than a half dozen) then you will run into some potential performance issues. Both in the front end web client when working with products as well as accessing products via the API. We are currently sitting at 8.7K individual SKU's with about a dozen custom fields. And it takes about 45 seconds to save a new/edited product on the web client.
ok, thnx for the tip