The menu to append the entry to.
The desired position for the new entry. Entries at or following this place will be moved. If pos is -1, the entry is appended.
The text to be displayed on the entry, in UTF-8 encoding, or null for a separator.
A combination of flags, some of which are mandatory.
the newly created entry, or null if pos is out of bounds.
Threadsafety: This function should be called on the thread that created the tray.
Insert a tray entry at a given position.
If label is null, the entry will be a separator. Many functions won't work for an entry that is a separator.
An entry does not need to be destroyed; it will be destroyed with the tray.