Chrome DevTools supports some useful keyboard shortcuts for easily incrementing or decrementing CSS values under-the-cursor. Shortcuts are available for both the Sources and Elements panels in Canary. In this quick 59s video, I walk through how to effectively use them.

For your convenience, I've also listed the shortcuts below:

Sources

Alt + Up/down: +/- 1

Alt + Page-up/Page-down: +/- 10

Elements

Up/Down: +/- 1

Shift + Up/Down: +/- 10

Shift + Page-up/Page-down: +/- 100

Alt + Up/Down: +/- 0.1

You can also find them listed under Settings > Shortcuts in Canary: