When you use the INSERT SPECIAL CHARACTER menu, a single click displays the character selected, and a second click is needed to insert the character into the writer document. This is not obvious and I think it would be helpful if the menu defined this option.
The online help for Insert Special Characters does not describe this double click function, but it is documented in the excellent LibreOffice 6.0 Writer Guide.
The help file: https://help.libreoffice.org/latest/en-US/text/shared/01/04100000.html
Seth Chaiklin committed a patch related to this issue.
It has been pushed to "master":
tdf#124105 - Document double-click to Insert Special characters
Usually takes 3-7 days after the commit before you can see the result.
Will mark as RESOLVED, but please REOPEN if you see need for other corrections.
Thank you for the change.