Practically every adjustment tool in the tool tab has the option to save adjustment settings as a User Preset. Most adjustment tools have a number of Built-in Presets. Each tool has a Manage Preset menu (i.e., three-bar icon) where you can access and apply the corresponding tool’s Presets directly.
The Built-in Presets may be useful in their own right or they can be used as an initial setting or starting point for that particular tool prior to further adjustment. In addition to selecting and applying the Preset to the corresponding tool, individual tool Presets can also be stacked. Although there’s no real restriction, in practice, this option is likely to be relevant to a small number of tools.
For example, you are unlikely to want to stack a number of sharpening settings, however, you may need to apply different combinations of keywords and IPTC Photo Metadata properties, such the Caption/Description writer, Creator’s Contact details, Licensor, and Instructions.
Both Built-in Presets and customized User Presets can also be accessed from the Presets Library in the Adjustments menu -> Styles -> Built-in Preset or in the Styles and Presets tool in the Adjustments tool tab. This option implies that you can see every Style and Preset available so you can apply each one from there. You can stack Presets by the tool and stack Presets with Styles. You can even create a User Style from a group of Presets or with a mix of Presets and other Styles.