Absolute vs. Relative Presets in Lightroom

Q: How to to create a Lightroom preset that adds +0.5 to whatever the current exposure instead of an absolute value?

A: Lightroom does not provide relative values in the Develop module. The Develop values are always absolute values, so Lightroom presets can only use these absolute values, such as exposure: 0.83 or red: 23.

However, the Quick Develop panel in the Library module does provides relative values such as +10% to the exposure or reds... But again not as a preset.