Place near the Spotlight icon Checkbox
Early versions of Tunnelblick placed the Tunnelblick icon near the Spotlight icon on the right side of the menu bar so it would always be visible, even if the active application had many menu items.
Later versions include a checkbox to allow the user to control the icon placement so it can be located where macOS would place it by default -- to the left of all icons existing at the time Tunnelblick was launched.
In macOS Sierra and higher, the user may move the Tunnelblick icon (and the other icons on the menu bar) by dragging while holding down the "Command" key, so there is no need for this checkbox and it is disabled.
On some other recent versions of OS X and macOS, the feature does not work properly if the user has selected "Displays have separate spaces" in the "Mission Control" System Preferences. This usually affects only systems with multiple displays, but it also affect some systems without separate displays. The checkbox is disabled in such systems.
In some situations, Tunnelblick does not know that the feature will not work, and so the checkbox is enabled and the user is warned if the setting might cause problems.