Given that you have a space in your directory name, "nature 2", I'm not sure you can do that.
If the name were "nature2", you set that in 12:Filter -> Mask:
but even that is kind of awkward.
What I would do would be to use
Everything to find your files, & drag the found files into BRU.
In Everything, a search for "nature 2" (in quotes) or \nature 2\ would find your files.
Note that "nature 2" would find (files & directories):
\nature 2\, a directory path
& also "i'm going back to nature 2.TXT", a file name
You can do all kinds of things to further filter results.
folder:"nature 2", would only find folders
parents:3 "nature 2", would find "nature 2", 3 directory levels down
(parents:3 acts
similar to, Lvl:1 with a starting search of C:\folder 1\)
So if you have:
C:\folder 1\nature 2\subfold 2\...
C:\nature 2\nature 999\subfold 2\...
parents:3 says to start the search 3 directory levels down
& since C:\nature 2\ is only 2 directory levels down, it would not be found.