Why do some of my vendors, items, and customers have (deleted) in their name?
When you see a vendor, customer, item, etc. with (deleted) at the end of the name, it means that while the record was deleted, it was linked to something else.
For example, let's say you delete a customer that has made purchases from you in the past. QuickBooks Online (and SOS Inventory) need to keep your invoices and sales receipts for that customer. So the customer isn't really deleted. It's just hidden most of the time. If you go to view an invoice with that deleted customer, it will show the customer's name with (deleted) after it, to remind you that you deleted that customer.
SOS Inventory can recover deleted items. To accomplish this, use the Deleted Items report (Operations > Reports > Miscellaneous > Deleted Items). To recover other objects such as customers or vendors, contact the Support desk.