Custom EditsBrowser Info Environment
Plz, check 'Instructions' page #18.
In 2.1.2- we used to keep the custom files inside the '\packages\theme_pixel\themes\pixel\css\less\' folder. But we learned during the process of upgrading, C5 removes the packages completely and then copy the new version. As a result, these custom files are lost during the upgrade process. In 2.3.0+, we decided to change the folder that houses these files. Now the custom files should reside in '\application\config\pixel_theme\' folder, so they would not be deleted on upgrade.
We will update the docs in the upcoming week, so you would be able to learn more on changes.