Hi,
The Markers are always placed on the inside by default (so if you defined the outside with the little sun to be on the right side of the screen, the marker will be placed on the left). In the basic door/window markers there are no settings to change this (they are this basic), but all the other markers have a "Flip" or "Opposite Side" option in their settings to change this.
As for the Flip being greyed out, for certain doors/windows flipping would not make sense in the other direction (like garage doors usually open inwards).
In this case, you have already marked the outside face with the little sun symbol, so we know where the outside is, and the lower (moving) part of a single hung window is usually the one inside. Double hung windows are just a spin on this, so the lower part is the inner part in those as well.
If you don't think these specific windows should work like this, please add it as a wish type post on this site to see if it is a popular wish, or talk to your local support/reseller to change this in future versions.
Regards,
Daniel Alexander Kovacs
Professional Services Consultant
GRAPHISOFT
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