I’m planning to do some night flying tomorrow on a IFR flightplan.
Rather than getting ASAP to my destination, I would like to overfly some cities.
I can create an IFR route which looks like what I have in mind, using Autorouter fly-by waypoints.
Now that results in a huge detour, which will look highly unlogic for ATC.
How do I manage to do this? Can I just ask to fly my route as filed? Do I need to put it as a REMARK in the FPL ?
Another option would be to file “some route”, and divert at some point.
One would say: Why don’t you fly VFR, because that’s the way you do scenic night flying.
Well… NVFR is not allowed in The Netherlands, so one must be creative 
Now that results in a huge detour, which will look highly unlogic for ATC.
They really don’t care. If you file your route and it gets accepted, they will let you fly they way you want to. Maybe they will ask you if you are interested in a shortcut, but this is about it. Many of our IFR training flights do not follow the shortest possible route (because we need some time for airwork and exercises along the way) and that’s perfectly OK for ATC. But it you care for some real (almost) uncontrolled night VFR, just cross the border to Germany and fly free as a bird
They really don’t care
I once filed from Osijek to Salzburg via Serbia. The tower guy was slightly disappointed when I insisted on flying the planned route because he had already arranged for lots of shortcuts. So a remark might be a nice thing to do so they don’t waste their time ironing out your route…
