SKULabs allows you to print scannable barcodes to apply tags to orders on the fly while picking them.
Go to Printing page > Tags tab and select the tags you want to print.
Choose the template you want to print to. Tip: Templates can be customized as desired under Printing page > Label Templates tab.
Once the barcode is printed, test scanning it into a notepad or text editor to confirm it is working.
Open any order and click "Start picking!"
Scan the tag barcode you've printed and you'll notice the order being tagged.