Some chars are difficult to enter, but this should probably be fixed by adding input methods for them. That is unfortunately is not easy as the present IME is language specific and does not allow general mappings.
(In addition the IME now opens on top of the button for edit switching.)
The full list of feedbacks can be found on w:no:Wikipedia:Torget#Flow (permalink)
IME options are possible. Esperanto Wikipedia has one on Flow. Also, have a way to insert special characters is possible via T93243: Flow's VE toolbar v2.
I guess "That is unfortunately is not easy as the present IME is language specific and does not allow general mappings." is pretty non-descriptive. This is about general mappings, especially of guillemets («») used as Norwegian quote signs. If we could replace a typed sequence foo "bar" baz with `foo «bar» baz', then we would solve perhaps 90% of the cases. A handfull of additional sequences would solve a whole bunch of remaining cases too. And yes, we can write IME replace rules for them, because I have already done so.
French language uses the same guillemets. I think there is some scripts to remplace it, but not sure. I'll check with the French.
Is the IME you have created used on no.wp?
This has stalled upstream, or in effect sort of declined, and I won't try to fix this again.