Only to a limited extent. If the glare is a fairly even, low-detail overlay, you may be able to reduce it by selectively darkening it, increasing contrast, and adjusting color so it blends better with the rest of the scene. But where the reflection contains real detail, you’re dealing with two images overlaid in one frame, and the hidden scene information usually isn’t there to recover. In those areas, fixing it often means manual retouching or effectively redrawing parts of the image.

The best solution is to reduce reflections when shooting, typically by changing angle/lighting or using a polarizing filter.

If a reshoot is possible, you could photograph the same window under the same conditions without the subject and try aligning/subtracting the reflection, though results may be imperfect. Similarly, if you shot multiple frames and the subject moved, those extra images may help reconstruct obscured areas.

So: mild glare can sometimes be improved in post, but strong detailed reflections usually cannot be cleanly removed afterward.