Thanks for the info.
If you have bookmarks located on the bookmarks bar, this message should go away. If you dont (or don’t want to), simply close the bookmarks bar.
Hit ctrl + shift + b (cmd + shift + b for macOS) to close the bm bar.
Ah ok now I got it how it works. Even if I hide Bookmark bar the new tap shows the bookmark bar but when there is no bookmark in the bookmark bar folder Brave offers me to import bookmarks. Better would be to complete hide bookmark bar, means from new tab as well.
We actually have an issue logged for this already:
Worth noting that you can do this with some (although I admittedly haven’t tested on that many) New Tab Page extensions if you have any installed. For example: