A few months ago, I switched from Vivaldi to Brave, just to try it out. Overall, it has been a positive experience, but I do wish there was an easier way to add bookmarks to the folder under the URL address field.
Please see the attached image from Vivaldi showing the ‘Add active tab’ feature. (Danish: Tilføj aktiv fane).
With Brave, there are several workarounds before you can add the same bookmark.
Looking forward to this feature 
Keep up the good work!
