Select I2: I 19.
Menu: Format-Conditional Format
In the pop-up dialog box, the condition 1? Select Formula on the left.
Right input? =I2=MAX(IF($D$2:$D$ 19=D2,$ I $ 2:I $ 19,))
Click the Format button to set the desired display format.
At this time, the highest branch of each class is displayed in a special format.