I can see the convenience of reactivating many vendors in one entry on QuickBooks Online (QBO), @RFT1. That's why I'm here to share details about this.

Currently, reactivating vendors by batch isn't an option. This is the system's way of making sure you'll be reactivating the right one. With this, you'll have to manually locate the vendor's name from the Vendors page and select the Make active option. You're able to easily identify the inactive ones since the term deleted is indicated beside their name. For the detailed steps, here's how:

1. Go to the Expenses menu.
2. Select the Vendors tab.
3. Make sure to select the Include inactive option from the Settings icon above the Vendors List table.
4. Locate the name of the vendor(s) you want to activate.
5. Click the Make active option under the Action column.

I've attached a screenshot below for your reference.

After that, I'd recommend pulling up the Contractor Contact List report. This is to verify that all your reactivated vendors are already included on the complete list of active ones. Just go to the Expenses and vendors section from the Reports menu's Standard tab.

Please know that you're always welcome to comment below if you have other concerns or follow-up inquiries about managing vendor accounts and transactions in QBO. I'm just around to help. Take care.