It should be able to hold 40lbs. I was thinking about attaching a
threaded rod to the wall and connect a platform to a linear actuator
sliding on the rod. This way the rod will do the heavy lifting. What
do you think? – chegov 2 hours ago
Here is what I think:
You mentioned stowing multiple items up there. If 40lbs is the max any one item would be less than that, say 15 pounds or so in order to leave a safety margin. I suggest that for lifting up the 15 pound items that a hoist, cable system, platform with linear actuator etc are far far overkill. You will save yourself a ton of money and avoid installing a butt ugly contraption in your kitchen.
You really should consider the folding step stool as suggested by Jasen or even a full fledged step ladder instead of the scheme that you seem set on. Even if you did some how manage to create your contraption you would still need a stool or ladder to get up there to slide the items onto/off of the platform.
Unless these items are ones that would be very seldom used there is a strong bet on the fact that you or others in your household would quickly get very tired of the inconvenience and time needed to deploy the contraption that you may very well stop using it.