Global adjustments picker key modifiers:Alt+Click = keeps picker activated in adjustment dockable panel after picking a color.
Command+Click&Drag selects any desired area instead of fixed (1x1, 3x3, 5x5, 11x11, ...) rectangle.
Ctrl+Tab on Windows, Command+F1 on macOS in Curves it switches between RGB/Lab/HIS/HSV. In Hue Editor it switches between Hue/Brightness/Saturation. In Levels it switches between R/G/B/All.Starting from 25.60b2 it switches between R/G/B/All in Curves, Levels and Channel Mixer.
Alt+Click to any button in Text Tool will apply settings to all text layer and ignore text selection. Levels adjustment picker key modifiers:Click = Set Pure White for Active Channel.
Shift+Click = Set Pure Black for Active Channel.
Command+Click (or Command+Click&Drag) = Set Pure White for All Channels.
Command+Shift+Click (or Command+Shift+Click&Drag) = Set Pure Black for All Channels.
Curves adjustment picker key modifiers:Click (or Click&Drag, or Command+Click&Drag) = Add point to currently used single channel curve and activates it (starting from 24.40b9)
Alt+Click (or Command+Alt+Click&Drag) = Add points to R/G/B curves.
Curves keys:Arrows keys allow to move points with normal steps.
Shift+Arrows keys allow to move points with precise steps.
Numpad [-] and Numpad [+] keys allow to navigate between points.
Shift+Numpad [-] and Shift+Numpad [+] keys allow to navigate between points and keep previous points selected.
Shift+drag allow to move points only vertically.
Command+drag allow to move points only horizontally.
Menu+Shift key to change Spline/Bezier and other modes for all curve channels together (starting from 24.40b8)
Shift+Text Input in Curves menu allows formula input (e.g. "x^2" or "sqrt(x)") (starting from 24.40b8)