Planning in hours

Yes.
Change unit in Global parameters.

duration is still in days (this will never change).
work is correctly in hours.

Pay attention : planning very small activities (< 1 day) can be much time consuming.
You may spend more time planning activities than working on them...

But you can plan.
Duration will be 1 day (the smallest in ProjeQtOr) but work can be less.
(don't forget that projeqtor is work driven)
In that situation, you should take care to define "apply strict mode for dependencies" to false