Need to cover stairs but still have access. Would like to use composit

I'm not sure what stairs you are talking about. I don't see any in this picture. Could you give us a little more information, please.

sorry, the stairs are behind the white pipe railing. It's a seldom used outside basement entrance ( in bad condition). Want to cover it, but be able to access it if needed. Thinking of a removable or trap door deck

Check you building codes first. They may require the stairs to be unobstructed. They are a form of egress if anything was to occur on the property like a fire.

You will need plans and a permit to build a deck, and only thing I could think of for access if allowed would be to buy one of those attic trapdoor ladder things to access the basement door corridor.

You could cover it with wood that you keep raised high enough to get out of the basement by the stairs. You could use a hinged door like they use in tornado underground shelters for egress. Keep the access, you never know when you may need it. Keep the stair area in decent shape so that it is safe, and the door from the basement usable.

You could make a cover for them. Like a mesh style that they use when making awnings. My friend has one that covers her stairs in the fall, to catch the leaves and acorns. She has a basement and stairs just like these. This must be a very large house!!!

How high are you thinking of going with the deck? Just over the stairs, say ground level? You could build around them, putting up a new railing, or covering the existing pipe railing. Or put in a planter box along that area of the railing so the open space to the stairs isn't as noticeable, but leaving the access still there and uncovered. Maybe add a gate at the stairs to prevent falls?