These destinations (mostly) have a further drop down box that gives further options such as Extensions/705anything that explains what each destination does/means such as "Incoming Route", "Extensions", "Trunks", etc.

Not so. This is inbound only.I assume that the list is all encompassing for use for inbound or outbound calls
I get that.The destination is where you want the call to go. Extension number, Ring Group, Announcement, IVR etc.
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