I'll write this in German 😃, where I use which value.
Aufgabe = Kundennamen
Beschreibung = Eigentliche Aufgabe (Meistens Jira Task nummer)
Details = Einzelne aufgaben die ich gemacht habe
Example:
Aufgabe = Kunde1
Beschreibung = jira-1234
Details = - excel erstellt mit allen werten
- Erstellung server in aws

timo By the way, in the "Export" screen you can already "group by work unit description" and then see the total time for each description. Maybe this serves as a workaround.
I would have to have a look, but it would also be one more step.
Currently I create the second task and then take the hours and add them to the first task and delete the second task.