I have seen that using the "Container" class in Genexus, when displaying the page in the browser, the "container" class of bootstrap also appears. This also happens with other classes such as "ContainerFluid" and buttons among others.
Now, where can you find this association and change it at my convenience?
Classes Container , ContainerFluid are documented here, and some others, which have a direct mapping with Bootstrap classes: Reference of Theme Classes used in Responsive Web Applications
In the Target Environment Directory you will find a file called gxtemplate.json , where these mappings are declared.
Although the architecture is designed so that in the future these mappings can be customized, currently (GeneXus 15) we do not offer a formal mechanism for developers to do so.