FILENAME
Returns the file name without directory as a string.
Syntax
string FILENAME(string fileName)
Example
FILENAME("C:\\mydir\\myfile.ext")
Will return 'myfile.ext'.
info
Remember to escape the backslashes in your file path, otherwise your expression will error.
You can pass the column name that contains the file path into the function instead of having a hard coded path.
For example:
FILENAME(FilePath)