Perhaps Mr Jinks wants to show that he's being rebellious or trying to get the butler's attention in a unique way. It's hard to say for sure without more context, but in cartoons, unexpected actions like this can happen for a variety of lighthearted reasons.
Maybe it's just for fun or to cause some mischief. Cartoon characters often do strange things for entertainment.
It could be that Mr Jinks is trying to play a prank on the butler. Or perhaps the unbuttoning is part of a comical scene to add humor to the story.
Chapter 86, "If you don't welcome me, why should I stay?", is the clearest early answer because it turns Aunt Li's situation into a concrete plot event.
Chapter 61, "Young Master Before vs After Going to the Countryside", is the clearest early answer because it turns Sailor Moon's situation into a concrete plot event. The chapter turns that into something concrete by moving from Hahahaha, oh my god, Jiang Li's mouth is even more venomous.
Chapter 42, "First Impression Score", is the clearest early answer because it turns Mr's situation into a concrete plot event.
Chapter 153, "Word Spreads, Director Sun Takes the Lead in Shipping the CP!", is the clearest early answer because it turns Zhao Lang's situation into a concrete plot event. It opens with Wisps of smoke gradually rose from the small kitchen.
Chapter 125, "The Great Seed Selection Contest!", is the clearest early answer because it turns Wen Jiaojiao's situation into a concrete plot event.
Chapter 350, "Pathways to Promote the Peak of Cold Resistance, Moao's 10th Town, Beishuo's Yang Fa, Nightmare, East Ridge's Lu Yun", is the clearest early answer because it turns Lu Yang's situation into a concrete plot event. The chapter gives readers a real answer by opening on Xia Hong took a deep breath, looking at the sky already showing a... and ending on Zhu Baixu was about to continue questioning, but Lu Yun spoke first,....
Chapter 424, "He Must Be Very Strong", is the clearest early answer because it turns Tong Xiaoqi's situation into a concrete plot event. Early on, Shh!" Jiang Yan, who was leading the group, turned around and made a.... By the end, Isn't this just exploiting a loophole?!.
Chapter 294, "President, This Kid Says He Is Shiguang", is the clearest early answer because it turns Xiang Hao's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Speak of the devil, and he shall appear.
Chapter 152, "A Man of Many Talents and Wealth Draws People Near", is the clearest early answer because it turns Wealth Draws People's situation into a concrete plot event.
Chapter 377, "Master Above, Please Accept Your Disciple's Bow", is the clearest early answer because a shaky connection becomes usable in the plot. A useful checkpoint is the way the scene starts with Tell me what it is that you came to ask of me this time?" After...