When I imported my library from a csv file that I exported from SAM, a bunch of songs that I know I'm playing didn't come into M1?

....check your mp3 tags.  M1 won't import song data from a record that has an empty Title field within the mp3 tags.  It is really, really important that you get all the tags in order, updated, corrected before you export the data to the .csv for M1 to import.  You can update the tags in SAM, but I always recommend getting a dedicated tag editor.  There are a couple I like that are MediaMonkey and Mp3Tag FYI:  both these tag editors will also export a .csv file that can be imported into M1.