The option that you're looking for is only available in QuickBooks Desktop. In QBO, you can record your purchased items as a whole or per piece and sell them per piece as well. You have the option to modify the quantity, for example, instead of putting 1, you can put 0.25, this isn't an ideal setup. However, you can still use this option as a workaround.
I would suggest looking for third-party apps online that can handle a retail-type of setup for your items.
If you have other questions, you can always go back to this thread.
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