There is no keyboard shortcut assigned to scroll through Presets Adobe Photoshop Lightroom Help | Keyboard shortcuts
However you can hover over your mouse on each preset and the Navigator will display a preview of the Preset effect.
You could request for such feature here Photoshop Family Customer Community
As Akash pointed out, there is no keyboard shortcut for scrolling through presets. Please add your vote and opinion to this topic in the official Adobe feedback forum: Lightroom: Ability to browse the presets and see its effects with the up and down keys. Meanwhile, you might take a look at the Any Preset plugin, which lets you preview presets at full size (not just in the tiny Navigator window) using the cursor keys.
Actually it's quite easy to fix on a Mac. Download Keyboard Maestro and create a simple makro. Start with selecting one preset - vit arrow keys up and down Lightroom undos the selected preset and applies next.
I use Keyboard Maestro a lot. It gives me the ability to set shortcuts to almost anything in any app. And I can set my own shortcuts everywhere. Couldn't live without it :-)
Start with selecting one preset - vit arrow keys up and down Lightroom undoes the selected preset and applies next.
As you repeatedly click presets in the Develop Presets panel, LR does not undo the effect of the previous preset. The only safe way to preview presets is to hover over the preset and look at the thumbnail in the Navigator panel, or use the Any Preset plugin to get full-sized previews.
You can easily prove this to yourself. Create a preset "Exposure" with just one setting, Exposure = +2. Create a second preset "Contrast" with just one setting, Contrast = +50. If you click Exposure and then Contrast, the photo will end up with Exposure = +2 and Contrast = +50, not with Exposure = 0 and Contrast = +50.
Many presets set some or all of the develop settings to their default values, so as you move from one to the next, you may not see the setting change (if it was originally set to the default value). You really can't tell which settings a preset will override without looking inside the preset's file to see which settings it contains (right-click it and do Show In Finder / Explorer, or use the Any Preset plugin).
Thats true. I have modified my macro in Keyboard Maestro to revert to original before applying preset. If I have made adjustments that I would like to keep before trying further presets I make a virtual copy of the image first.
Here is a link to a video where you can see exactly how this is made – creating the macro and when I am using it: