Patio door windows:How can I cover them to stop cold air?

https://home.howstuffworks.com/green-living/insulate-sliding-glass-doors.htm

A very popular topic this time of year. For less than $15 you purchase a patio door shrink film kit. Amazon or anywhere that sells insulation materials. Clean and install the double-sided tape all around the door. Stick the clear film to the double sided tape. Using a hair dryer heating different areas will cause it to shrink, removing all of the wrinkles.

You won't be able to use the door, but the film tears off easily in an emergency. It is not reusable but so worth the expense during the dead of winter.

https://www.hunker.com/12001883/how-can-i-insulate-a-sliding-patio-door

I got a spring-tension rod, found two shower curtains I liked and hung them in front of it - they're long enough to 'pool' on the floor which keeps the cold from getting in underneath them and if I want to open the door, I just slide them along the rod as far as I want - has worked like a charm for almost 10yrs now...

I would google search Insulated Window covering and you will get a ton of ideas of something you can pick up or order.

You have to install curtains, panels ( blackout or insulated) to keep the cold air out. We also roll a blanket in put it at the bottom of the door, where the track is.