There is only one file type that uses the .LRSMCOL extension:
Adobe Lightroom Smart Collection Settings File
Settings file created by Lightroom, a photo editing program; stores settings for a Smart Collection, which categorizes digital photos based on user-specified criteria; helps organize large amounts of photos into manageable groups.
LRSMCOL files can be imported and exported using Lightroom's Collections panel. Right-click a Smart Collection and choose "Export Smart Collection Settings..." or the "Import Smart Collection Settings..." option.
NOTE: Lightroom was formerly known as Photoshop Lightroom.
Updated: April 6, 2018