Replace theme in Mendix 9

What is recommended way to completely replace my theme with an atlas 3 theme? Subject is a module development project and the theme is not important. The upgrade procedure as described in the documentation is quite extensive. IMHO it needs a conversion wizard. When a delete all theme* folders and just download atlas core from the marketplace the pages have no styling at all. I would have expected a simple way to choose and apply a theme from the appstore. Is there any technical description how Mendix 9 works with styling? EDIT:
2 answers

You mean: If you have no or little modifications to your styling, it is not a big task to migrate. If you have lots of styling, it might be an option to add a link to your Atlas2-styling in theme/web/main.scss, but that is not the recommended way.

So far I like the extra possibilities that the new set up provides: you can add styling to a module now.


Just one extra tip: when having a project originally based on Atlas 2 (even when created for Mendix Pro 9), your settings.json is likely to have “cssFiles”:  ["styles/web/css/main.css"]

This needs changing to include "theme.compiled.css" for your themsource style modifications being picked up by the Mendix Pro 9 and compiled into CSS.

for example to:

    "cssFiles": [