MagicPicker lets you pick colors halfway between foreground and background using F/B slider. Click on the eyedropper on the slider to pick current foreground/background colors into gradient from Photoshop. Then move slider to acquire intermediate colors.
Add/use more sliders in MagicPicker!
Works in Photoshop & Illustrator CC 2023 and below!
From series of tutorials for MagicPicker, advanced Photoshop color wheel and HUD