I've seen a few posts about this, but no real solution yet. I'd love to be able to import downloaded csv's from RR into SDR#. Where are those freqs. stored, in .db, .xml, or .cfg files? This would be a great addition to Frequency Manager.
A .csv (comma separated values) file is quite editable with applications like Excel or Notepad. You might be able to edit a db file in Access, a ..xml file in Word or in any number of apps such as the excellent freeware called Notepad ++ (plus plus).
The real issue here appears to be a lack of knowing how to do imports into SDR#, not editing the source files.
The only time I use a csv file is using GNURadio. More specifically op25. There should be a plugin already in SDR# natively called frequency manager to store frequencies and label what that frequency is. As of right now i don't know if there is any reason to import a csv into SDR#. If you are doing PS scanning you are using DSD+ or GNURadio.
I have solved this problem by examining the file that the SDR programme makes when you add something to the internal database. Manually add some frequency and station info into the SDR then extract and examine the files for the database and open it - sometimes you have to add ".txt" to the end to make it readable. If it's gobbledygook you may be out of luck. Make a note of all the blanks, commas or other place markers then add a set of your own data, remove the "txt" suffix and see if it works. I assume (careful!) that you are reasonably proficient in Excel and digging into the files in your computer.