To add a folder to favorites, I know 3 ways (maybe there are more) :

While navigating, right clicking on a folder has an « add to favorites » option.
And you can find that option from within the folder in the file menu.
You can also right click on an empty space while exploring a folder.

I miss a couple of important places, where I naively looked for that :

• The breadcrumbs : I tried to right click, not only on the long line of files, but in the empty space.
• I also wanted to drag and drop one folder from the breadcrumbs to the favorite panel
• Right click in an empty space in the favorite panel to add the current location (if available, not as a search result)

Do you think that would make the feature easier to use ?

I added an image with green : places where I can add to favorites, red, places where I first looked to add the current location to favorites :) (more instinctive, closer to what's happening on macos or windows)