How can I easily specify an or-search in Finder? I wanted to create a smart-search for my R-files, including both files ending in ".r" and ".rmd". Obviously, files can't end in both.

This yields only files that satisfy both criteria


This yields no files because the criteria are mutually exclusive.


How can I search for files ending in either .r or .rmd and more generally
how can I specify "or"-searches/ disjunctions? Using "or" or "||" didn't do the trick.
Operands must be written in capitals, so they are understood as such. Therefore, using OR instead of or, will do exactly what you want.