Currently its description is embedded in the LibreOffice - Security page, and makes it quite crowded:
Also it might help the smaller problem reported in bug #100096 :
In the Security Options and Warnings dialog pressing Help/F1 while OK, Cancel or Help is selected, it'll give totally uninformative results like this.
Gabor Kelemen committed a patch related to this issue.
It has been pushed to "master":
tdf#105280 Split out Security Options and Warnings help page