How can I categorize all the expenses from the same vendor at one time?

Thank you for reaching out to us here on the Community page, @holtlegacy.

If the expenses are manually added to QuickBooks, you can categorize them at once by following these steps:

1. Log in to your QuickBooks Online account, then click on Expenses at the left pane.
2. Select Expenses beside Vendors.
3. Check the box beside the Date column for the transactions you want to categorize.
4. Tap on the drop-down arrow beside Batch actions, then select Categorized selected.
5. Choose a category, then hit Apply.

On the other hand, if the transactions are downloaded from your bank, you can categorize them by following these steps:

1. Click on Banking at the left pane.
2. Look for the expenses you want to categorize, then check the box beside the Date column.
3. Choose category.

You can also open this link for additional reference about managing your income and expenses in QuickBooks Online.

Thank you for allowing me to help. If you have any other questions, leave a comment below. I'll get back to you as quickly as possible. Have a good day!

@Angelyn_T 

"On the other hand, if the transactions are downloaded from your bank, you have to categorize them one at a time from the Banking page."

Also, from the Banking page, you can select the batch to categorize expense transactions.

Select Expense transactions boxes and select Batch actions and select Modify selected from the drop-down and categorize account as you need.