Presets for Affinity Photo Adjustments ?? You can find it in the view menu and studio in adjustment. Create and use them in your projects super easy
The panel has limited functionality and displays all the existing by category such as vibrance, HSL, gradient map, etc. Some have only a default which is fine as you can use it do apply the effect and perhaps there are limited options anyway or it makes little sense to have values stored. However, some have more options available and you can click them and that will either add a new adjustment to the layers if nothing is selected or if the one selected is different from the clicked (such as a gradient map and HSL say). If you have one selected and it is a gradient map and the new one is a gradient map, it will just replace the settings in the current selected entry. The image will then be modified by the effect and you can then continue to edit the settings but this will not affect the stored preset.
You can right click the entries in the panel and delete the entries as well as rename them.
If you open an image of a cat then the panel will display the effect applied to the cat or dog or house etc.
When you are using a gradient map or HSL as a layer, you will see the various settings such as blending mode, opacity, color options etc and you will see a 'add' button in the top left, click that with the current settings and that will then prompt for a name and will then add it to the panel. You will see the entry appear in the category so if you are creating with a HSL entry then it will appear in the HSL category and will show an image of the effect. The settings for the panel are stored, all the settings so if you have been using the blending mode set to color burn and an opacity to 50% etc then those values are also stored to the panel.
You can, of course, still just use the layers menu to use all these live color effects. The panel just makes it easier to add these color effects and see the result before you decide. Youtube video on subject
You decide that you want to create a threshold effect where the color image quickly becomes a black and white (only) image. You can go to the layers menu etc but you can quickly just go to the panel and click on the first entry or the third and add the black and white. The settings panel for the threshold also appears and you can set the value such as 10% for a very white image or 90% fr a very dark image. You can also use the opacity to see more of the underlying image or less (set to 0% to see the image as before). You can also set the blending between the threshold and the original image. You can run through those and select overlay, divide etc depending on what you want to achieve. The darken / multiply etc will result in a darker threshold effect, the lighten / screen etc in a lighter result and the others are more esoteric but the difference and divide are always worth checking out. There is also a little gear in the bottom right corner where you can modify the underlying (bring more of the original back) You also have color channel features and coverage maps. Sadly, when you save your settings not all of the settings are saved such as coverage map etc