daniloppp I haven't find references on which class/file should I play with?
First of all it's doable as you can see at my forum (Moccato). Then again it's not a one-liner of CSS.
My best advice: Use the inspect element function of browsers like Firefox and Chrome to explore the structure of the DOM and play around with it. Most of my work of changing stylesheets is done that way. Once I've achieved a certain aspect, I transfer the changes to the custom CSS in the admin panel and approach the next step.
In the case of the categories list you will find them in a nav element with the class of IndexPage-nav, DiscussionPage-nav, UserPage-nav etc. To shift it to the right I've applied:
.IndexPage-nav:not(.TagsPage-nav), .DiscussionPage-nav, .UserPage-nav {
float: right;
width: 8.5vw;
}
But that's just the first step as you may find out once you apply that to your forum. The next step will be to provide the space for the nav element now moved to the right:
.sideNavOffset {
margin-right: 12vw;
}
But even that is not enough to have a convincing look. You need to adjust a couple more aspects, that would be to much to list here. So take this as a first hint where to start and experiment yourself. In the end, that's the most fun too.