Let's say I create a video game. Let's call it V.
Then I set a rule in V that you need to find a car in the game and click on it to jump.
Now we ask the question of how to jump on V.
Someone replies that you can do so by clicking on a car. Is this proposition an objective truth?
The statement
One can jump in V by clicking on a car.
is a true proposition.
That the game V has been created by a human person is not relevant for the question whether the proposition is true.
Aside: In general “truth” means “objective truth”.
We change our world -- our shared objective reality -- through our actions. In that sense, every such action creates, for everyone, a new reality and new truth.
In your example you created a video game -- but it does not need to be this complicated. If you simply put a book on your table, you also create a new truth -- "a book lies on my table" becomes a true statement.
Is it possible for truth to be set by humans?
Humans are nothing special, regarding discussions around truth or objectivity and so on. Humans are a regular part of the universe; they do not stand "outside" in any fashion. We have a bit more "features" than the other inhabitants of our particular planet, as far as we know, insofar as our brains are developed enough to observe and philosophize, but that is only a statistical outlier, so to speak - there is no universal rule that says that we humans must be the only such beings in the universe.
Everything humans do that affects the world in any measurable way is part of reality. If we create a computer game, which is absolutely a bog-standard object in the universe, on every level down from the electrons powering your computer to the in-game rules like clicking cars to jump, then all statements that accurately describe it are as true as any statement about a stone or an apple.
So yes, it is possible for truth to be created by humans, in the sense that humans can and do influence the world, and every measurable outcome of such influence can be uttered as a proposition, and using measurements, every such proposition can be assigned a truth value. The question of whether the car is a real, physical car, or a data structure inside the RAM of the gaming PC, or a visual representation on the PC's monitor, does not matter, it is all physically real. The bits in RAM describing the car (and the logic, e.g. the program code) are physically in the machine (in the form of charge within capacitors and whatnot). The image on the screen is physically there (it emits photons). The program code is physically there (again, as storage within RAM). Its physical representation deviates from a car made from metal, of course, but nonetheless, it is in all senses and on all levels physically real.
A video game is a virtual reality. Within the game, the rules of the game are truths that one must obey to navigate the game. These truths are objective within the game. The game provides the rules required to play. One does not need to memorize every line of code written creating the game to navigate the game. That code is part of the real world and outside the virtual world.
Outside the video game, game rules have no meaning or context but the video game itself (in the real world) has real purpose: entertainment. So a different set of rules apply like: The game cannot be played unless the game hardware is powered on. The game cannot be played until the game software is installed and activated and other installation and activation rules. These truths are meaningless in the virtual world.
But, in order for more than one person to play the game and be able to share the experience, players in the "real world" must have an objective set of truths regarding the game that includes both real world and virtual world truths.
Hope this helps. I wasn't sure if I interpreted your question correctly.
Trueness of that statement is undefined, as the statement itself is insufficiently defined. That is was made by a human is irrelevant. It is a statement about the behavior of a system, a system which itself is designed to have certain behaviors.
In the colloquial sense, understanding the implicit context, it would be true (and "objectively true"). The only thing that could cause someone not to consider it an "objective, absolute truth" is the informality and the incompleteness of the statement. This was brought up in other answers and sparked some discussion in the comments.
An absolutely true statement that describes an invariant, always-true behavior, would have to be something along the lines of:
"Given this game [define what a game is], defined by this algorithm [define what you mean by algorithm], as long as the laws of physics are valid [list the individual laws that it depends on], and the machine is not interrupted in running this algorithm and does so without errors [clarify what that means], clicking on a car [define what clicking on something means] always leads to the in-game character jumping on the car [define what that means]."
Or if the described behavior needn't be invariant, and more in-line with what the true meaning of this natural language statement is, the objectively true form of it would be:
"A person able to comprehend this statement and living around year 2024, and familiar with concepts of video games, cars, etc, will agree with the notion that clicking on the car generally leads to jumping on it, even if there is an arbitrary number of special cases where this might not happen"
The question as posed asks about objectivity of truth of statements about human-made stuff, but the complicating factors around it are based in non-exactness of human language (form of the statement, not its true intended content), and blatant disregard for the simple truth this statement requires an enormous amount of context to make it even possible to assess its trueness in the logical sense.
I'm being deliberately provocative here in hopes that it answers the question but:
Urm, yes.
You made the game, you made the rules, you made the truth.
