This script will set the bookmarked playback pointer of the selected tracks (established when a track is set to "Remember playback position") to 0 seconds, effectively clearing the bookmark.
Perhaps Also of Interest...
downloaded 1m 18s ago
Drag-and-drop to convert audio files with iTunes
downloaded 18m 40s ago
Exports and then re-imports selected tracks' artwork
downloaded 41m 48s ago
Copy files of tracks to selected folder
downloaded 49m 7s ago
Use tag data to formulate new file name for selected tracks' files
downloaded 1h 33m 49s ago
Perform search-and-replace on text in your choice of tags
downloaded 1h 54m 51s ago
Batch-change the Album Rating for the albums of selected tracks