The boy had also sketched a picture of a shrapnel-filled improvised bomb left on a city street and exploding, a jury heard.
The boy, who cannot be identified for legal reasons, has pleaded not guilty to acts in preparation for a terrorist attack and is facing trial in Brisbane Supreme Court.
The jury on Wednesday heard the teen had downloaded an explosives manual from al-Qaeda in the Arabian Peninsula, a group proscribed as a terrorist organisation.
The manual was titled "how to make a bomb in the kitchen of your mum", former counter-terror officer at Queensland Police Steven Gibb said.
The manual instructed on how to build a bomb with a casing that would be "turned to shrapnel flying at high speed" when it exploded, Detective Sergeant Gibb said.
During a search of the teen's parents' home in September 2024, officers found his diary with a sketch of a household device he labelled as "filled with shrapnel and explosives", the jury heard.
The teen also labelled the sketch as being left on Boundary Street and exploding, Det Seg Gibb said.
The jury previously heard Brisbane's Boundary Street was on the route of the city's Labour Day march that usually attracts 20,000 people.
The teen is accused of planning to use pipe bombs packed with nails to attack Liberal Party members and the march to promote beliefs he shared with America's notorious Unabomber.
The jury had earlier been told the teen considered Mr Dutton as a potential target.
Images and memes celebrating the Unabomber - US terrorist Ted Kaczynski - were found on the teen's digital devices, Det Sgt Gibb said.
The teen declared the Unabomber as "the GOAT (Greatest Of All Time)" in a text message to a friend.
He wrote in his diary about having thought for years about carrying out a mass stabbing attack in a shopping centre and was surprised when a similar massacre occurred at Sydney's Bondi Junction.
Under cross-examination by defence barrister Laura Reece, Det Sgt Gibb said the teen had been subject to emergency mental health action and had written about having hallucinations.
"I heard voices. They were people from my classes. It was like I was dreaming but I was awake," the teen wrote.
The teen wrote in his diary of how people likely looked down on him as a "struggling artistic child" and his father took away his digital devices out of concern he was losing touch with reality.
"Apologies for the edgy unfunny memes sent in the last couple of months," the teen told his online acquaintances in a group chat.
"I will likely come to view these memes the same way I viewed my unfunny Nazi memes in 2021."
The teen later wrote in his diary that his interest in the Unabomber was "psycho".
The trial continues.
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