Code:
tell application id "OFOC"
tell sidebar of front document window of default document
set lstProjects to value of descendant trees where selected = false and class of its value is not item and class of its value is not folder
end tell
end tell
Filtering out objects which return a class of
item just excludes non-data items like the Inbox and Library nodes in the sidebar tree, and various grouping labels in the content panel.