Thanks for that! I've sent you a slightly more detailed email response with the solution, but just in case anyone else has a similar problem:

On Windows, the install location for ArtRage contains only ArtRage's default presets, so placing additional presets here will not add them to your preset collection.

The location for custom presets is in application data.

To get there manually:

Run 'appdata' then go to Roaming, Ambient Design, ArtRage

Within this folder, you will see 'Content'. Open the Content folder, then Tool Presets. This is the location for all your custom tool presets, and when you create any new tool presets, they will be added to the appropriate folders here.

To get there from the app:

You can more quickly get to your user content folders within ArtRage via Tools -> Browse Content Folders. Choose 'Tool Presets Folder' in that menu

You can find some more detailed information about porting all your ArtRage 4 data across to ArtRage 5 in Artrage's install folder in a document 'Copying Old Custom Content.rtf'