When the "Copy Line Descr. to G/L Entry" is selected in Sales & Receivables setup or Purchase & payables setup the posting of a document will create entry for each line. If not selected then posting will combine the lines and just create 1 entry in GL entries.

It should be possible to combine the lines and keep the description instead of using "Invoice XXX" as description.

Usecase:

Customers maybe buy coffee for the office, get 10-15 lines on the invoice(good selection of coffee pods) but all are posted to the same GL account with the same description "Coffee for the office".

When posting the purchase invoice you either get a entry with description "Invoice xxx" or you get multiple entries all with "Coffee for the office" as description.