I am contemplating switching to Klok from a cloud-based time tracker because I really like your user interface.
However, the current version doesn't seem to support adding categories of work to projects. My current software allows me to specify categories of tasks to each project (specified for each project separately according to requirements).
E.g. one project combines tasks that can be categorized as "administration", "marketing", "sales. A second project shows categories such as "project management", "design", "development", etc.
These come in really handy to get a grip on the time allocated to each category of tasks, whilst still being able to see the total project time.
Working with subprojects doesn't do the trick because the sub projects are not totalled in the total project time.