You can open to add water, but I use a piece of aquarium tubing and add it through the vent holes. Someone on here showed me how to take a squeezable (disposable) water bottle, cut a hole in the lid, stick the aquarium tubing through, and seal it with hot glue. Then you can fill the bottle with water and squeeze to fill your rags/sponges/water wells during lockdown.
I do open the incubator twice a day once they start hatching to take babies out. This is against popular theory on lockdown, but I find leaving them in causes more problems than taking them out. I just make sure I raise the humidity as high as it will go before opening, and make sure all the sources of humidity are full of water so they'll re-humidify quickly after opening, then I work quickly and close it back. I rarely see much of a dip in humidity.