Here is a recent topic on something similiar:
Hopefully that discussion is around exporting from another application and importing into Solarwinds for first time. If you have nodes already in Solarwinds with outdated information, it depends what you are trying to do. You cannot do it from CSV files or anything similar, but you can make node properties changes to several nodes at once using the GUI and can also update via SQL as long as you can design the query to do whatever it is you are looking to do.
I realize my last comment regarding SQL may be a little confusing, so as an example you can use node properties to add a custom property to certain nodes and set the value to X. But if you want to rename all switches that start with "ABC" and replace with "XYZ" but retain the room number for example, that is a SQL thing.