PROBLEM: Sliding-glass door gets balky in sustained cold (below 10 degrees F) weather. Either it won't open or or it won't close tight. Usually because ice and snow jam the track or lock.
SOLUTION; First, clear away as much snow as possible, using a small scrub brush. (DON'T chip away at any ice at this point; you could damage the window, frame or track.) Second, put a quart of RV water-system antifreeze in a teapot and heat it to about 120F (I use a kitchen thermometer for this report, but all that's needed is that the fluid feels warm as bathwater.) Third, pour the antifreeze sparingly on the likely trouble spots, gently chipping away any ice which remains. Finally, make sure the slider-track and its drain holes are free of debris.
CAUTIONS: Do not use automotive anti-freeze, which is made for engines and kills pets. Do not overheat the antifreeze; just get it warm. It includes alcohol and other (nontoxic) stuff which might do interesting things if boiled. Use it sparingly to avoid damaging glass, plastic and any insulating felt. (Again, the stuff is NOT toxic or corrosive, but sudden warming can weaken any material.)
ADVANTAGES: The anti-freeze is not toxic or corrosive, so nothing gets damaged. It won't make pets sick (different from automotive anti-freeze). It temporarily lubricates the door track. (Use WD-40 later?) There's really not much need to clean up afterward, which is often a challenge in the cold. Best of all, it seems to work every time.