I'm sure there are so many topics about this subject, but I could not find any of them ... so sorry for asking it again (I know I should improve my searching skills)
I will format my computer ...
My images and Lr catalog is on another drive.
I also have my Lr settings with my catalog.
So, I will take my plug-ins.
Other than plug-ins ... the only other thing I have to back up is the preferences file, isn't it?
Any other thing that I should back up?
By the way, are smart collections (and other types of collections of course) saved with the catalog?
Collections only exist within the catalog. Collections are simply pointers to your images. A collection does not actually contain any images, just pointers.
Thanks ... so it seems that I backed up every Lightroom thing before formatting.