Hey again, Vhumpal,
I actually just responded to your direct message before seeing your comment here. You should already have this information I'm about to share, but in case you haven't seen my message, I'll go over the options for sending emails in QuickBooks Enterprise and QuickBooks Online here as well. Hopefully it'll be helpful to someone else, too!
QuickBooks Enterprise is another version of QuickBooks Desktop. Given that, the Enterprise 20.0 version does also have the option to send a single email for multiple invoices. All you'd need to do is follow the same steps as I gave above. Here are those steps again though for ease of access.
More details about this can be found here: Email sales forms in QuickBooks Desktop
When it comes to QuickBooks Online, that version of the program works pretty differently than its Desktop counterpart. The option to send multiple invoices or transactions in a single email to the customer isn't yet available. The option to send multiple transactions at once is there, but the transactions will be sent as individual emails. Here's how to do that if you're interested.
To share your interest in seeing a similar feature to the Combine forms to a recipient in one email in QuickBooks Online, follow the steps in this article: How do I submit feedback? If you don't have a QuickBooks Online account already, I'd be happy to pass on the feedback on your behalf.
I hope that helps!