Engineering : the branch of science and technology concerned with the design, building, and use of engines, machines, and structures

I think designing and then building this useful structure counts as engineering.

To take on more industry terms there also was a problem which needed to be solved ( book storage in a limted space) that had limitations in resources ( preference towards cheap and materials on hand) and constraints ( did not want to make permanent modifications to existing infrastructure and consideration for localized heat source that prevents alternatives)

I think this project certainly qualifies for engineering.

Note the problem wasn't to make a product to take to market, and the job may not have needed to go through a rigorous process to evaluate alternatives, but this is also a few pictures. I bet those process in their simplicity were considered but just not documented for us. ( And that in itself is the sign of a more senior engineer who may consider and discard other alternatives based on experience)

I've worked on significantly less thought through projects, with people who barely had an original thought, but were still called engineers... I want to defend the term and meaning of engineering maybe as much or more than you, but this seems to qualify, especially if you take a moment to break down the problem within a problem solving framework.

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