First, you don’t necessarily need to replicate the full details of the supplier’s invoice in the QuickFile purchase record as long as the overall net and VAT totals are correct - in the event of a VAT inspection the inspector won’t care how you’ve represented it in QuickFile, they’ll want to see the original VAT invoice from the supplier and confirmation that you’ve put the right totals into your VAT return. I run a retail shop and often have invoices from my suppliers with 100+ individual lines, and in QuickFile I just record one line “Goods for sale” with the net and VAT totals.
Second - you almost certainly don’t want to use “Stock” as the purchase category, that code (along with “finished goods” and “work in progress”) is only really useful for end of year adjustment journals. If the items are ones you’ve bought to re-sell then use “General purchases”, if they’re tools you’ve bought for use within your business then either an asset code like “Office equipment” or an overhead code like “repairs and renewals” or “premises expenses” might be more appropriate. Your accountant can advise, but for low value items (say under £100) I’d tend to make them expenses, and keep the asset codes for higher value items that it’s worth depreciating over several years.