Cascadea 2.1.3 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The program lies within Developer Tools, more precisely Webmaster Tools. This Mac application is an intellectual property of Michael Freuden.
From the developer:
Cascadea is designed to help you customize any website. Cascadea is the native custom style extension designed exclusively for macOS and Safari. The tool lets you customize practically any website using custom CSS themes. Therefore, you can make your social media feed pop with your favorite colors. In addition, you can give that super-bright website a darker theme that's easier on the eyes.
You may want to check out more Mac applications, such as Url Extractor X, Navicat for Oracle or JustinmindPrototyper, which might be similar to Cascadea.