Hi Linda177. Yes, it is still possible to add a delayed charge to an existing invoice. Once you create the delayed charge, open the invoice, and the charge will appear in the Suggested field on the side of the page.
In the new display, the workflow has shifted to a suggestive sidebar. If it isn't showing transactions automatically, you may need to enable the Automatically show suggested transactions feature in your settings.
You may refer to this screenshot for visual reference.


After adding it to the invoice, check the top of the page for linked transactions.
Reply here below if you need anything else. We're here to help.