Is there a way to have a Task-list view that allows to group entries
(e.g. based on categories) but each group's sort order to be
user-defined?

E.g. I am using categories "home", "office" and I like to group items
accordingly (and to "collapse" those that are currently not of interest)
but be able to order items within each group according to my own
preferences (in essence priority or execution order, but without the
hassle of assigning prios etc.)

Hope I could make myself clear...

Michael