How to cover a doggy door panel attached draped patio door?

I have a similar set up. You can use velcro. Close the drapes, then pin up around the doggie door, then on the backside use washable fabric glue to properly place the velcro, dots or strips to keep open when needed. This way you do not have to permanetly alter your curtains.

You could also try a Command hook (sideways) to catch the drape and keep the door accessible.

Perhaps sew a snap onto the drape, one half down at the bottom corner, the other half up a bit higher, so you can just turn the corner up and snap it in place, out of the way of the doggie door. When you don't want puppy to have access to the door, just unsnap the drape and let it fall into place.

I would close the drape and mark where the dog door is... then I would cut a slit in the drape (kind of like the slit in a straight skirt) where the center of the dog door is and as long as the dog door is tall...

To finish the raw edge: Take the stitching out of the drapes hem about 6 inches on either side of the slit... unfold the hem.... on the 'right side" of the fabric...stitch bias binding bias tape along each edge of the slit.. straight up, do not turn to go down the other side and stop stitching at the top edge of the slit.. cut off bias about 1/2 to 3/4 in above the slit. Turn the bias to the wrong side of the slit, press and/or pin in place folding raw edge of bias under. Hand hem (or use fabric adhesive) to secure in place... re-stitch hem and you are done..... you have access to the dog door thru the curtain.

why not do something very simple! use window film on your dog door panel, like these from home depot. some very beautiful scenes! then just close your curtain or verticals as far as the door opening! no need to alter your curtain or cover up the dog door!

https://www.homedepot.com/s/window%2520decals?NCNI-5

https://www.homedepot.com/s/window%2520film%2520for%2520sidelights?NCNI-5

i especially like the mosaic and cut flora ones. they should fit the width and length of the dog door panel ok.

All the suggestions so far are quite doable. If you want more privacy on the doggies door flap you could try privacy window film. It would diffuse the light coming in during the day and obscure the view from outside at night (when the lights are on inside offering a clear view of homes interior).

In the same situation, I ordered a matching 63 inch drape for that segment.

If you aren't looking to cut out the light so much as just providing privacy, I'd just buy a $3 bottle of Gallery Glass and apply it to the window portion of the door. It is quick and easy to apply, removes easily when you want to, and comes in clear and a variety of colors. Adds enough texture to diffuse the view from outside. I love this stuff and use it in a variety of situations and, NO, I have no connection to the company that makes it. Find it at craft stores or online from Plaid. Good luck with your project.

I would mark the center bottom of the dog door with the drapes closed. measure to the top of the dog door. Cut a rectangle of fabric about 6 inches wide, and an inch taller than the dog door. Sew it in place on the front centered by the mark at bottom. A narrow upside down v. Cut in the center, turn to back, and sew in place.Dogs can walk through, but covered inside and out. Barely noticeable.