I am in the Logic Event List and I have 100 notes that I want all to have 127 as their velocity but all the notes have various velocities. Is there a command that allows me to change them all in one hit to 127?

There are various ways to achieve this:
Give the correct value to the first event and use a key command for the feature: “copy value to following events”
Or
Select all the 100 notes you want to change, and while you point your mouse to change the velocity values, hold down the Option and Shift keys [Ctrl-Shift] while you change. All your velocities will assume the same value.
Or
Select all the notes, double-click on the velocity of one of the selected notes, enter the new value numerically via the keyboard, hold the Option-Shift keys [Ctrl-Shift] and press Enter or Return [Enter]

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