Check out section 25.5.1 in the Music Braille Code 2015.
The left hand pizzicato is indicated by placing dots 456, 345 (left hand piano sign) before each note so marked. It can be doubled if four or more notes are affected. An octave indicator is required after this sign, as is a dot 3 if the next sign contains a dot 1, 2, or 3.
The words "LH pizz." or "m.g. pizz" are omitted unless you are doing a facsimile transcription. Likewise, the plus sign above the note is omitted (example 25.5.1-2 shows this).
You'll probably want to list this on your special symbols page.
Thanks for a great question!