As of this time, there isn't an option to group all billable expenses into one line on an invoice. But I've got a workaround for you that you may consider.
You can total the time of each product and enter a single time activity to add it to the invoice as a group. Here's how:
Click the Plus (+) icon.
Select SingleTime Activity.
In the Name drop-down, select the vendor.
Choose the customer from the Customer drop-down.
In the Service drop-down, select the appropriate product.
Put a checkmark beside Billable (/hr), then enter the rate per hour.
In the Time field, enter the time of hours.
Click Saveand close.
However, you'll have to repeat the same steps for the other products.
Once done, you can now add the billable expenses to the invoice. For more guidance, you can check out this article for your reference: Add Billable Expenses to Invoices.