Script: Batch Append Text to the Description of a Photo
Photos 1 to Photos 3.0 on High Sierra does not support to append a text to the descriptions of several photos at once.
To batch append some text to the descriptions of selected photos you could try a simple Apple Script.
Select the photos in Photos, then run this script from Script Editor or the scripts menu. The script will ask you for text to be appended to the current description.
-- Batch append a text to a description, author: léonie
set toAppend to text returned of (display dialog "Enter the new caption: " default answer "" buttons {"OK"} default button "OK")
-- batch change the description to the input
tell application "Photos"
activate
set imageSel to (get selection)
if imageSel is {} then
error "Please select some images."
else
repeat with im in imageSel
tell im
if exists {its description} then
set old_desc to get its description as text
else
set old_desc to ""
end if
if old_desc is "missing value" then set old_desc to ""
set the description to (old_desc & toAppend as text)
end tell
end repeat
end if
end tell
return imageSel