One menu is called "Override Linuxconf's addons," while the other is called "Create Linuxconf's addons." Both seem to point to the same menu. There is a very small but important difference:
The "Create" menu is used to edit the add-on file in
/etc/linuxconf/control. The "Override" menu is used to
edit the same file, but the changes are not stored in the file
itself, but in the /etc/conf.linuxconf file. So the
"Override" menu is used to do local changes. The "Create" menu
is used to manipulate the add-on directly.
If you do not intend to distribute any dropins, the difference is moot. Always use the "Create" menu.