Extend Tool: Won't let me extend past a certain point

[TenbarCreative]

Okay, I have the Extend Tool bracket at the right side of the recording in Multitrack.  I'd like to extend it out further so I can more clearly do my fade in/fade out, but bracket only let me go out to roughly 1 min.

Why can't I extend further?  Or can I only extend in Edit "mode" if I want to trim or eliminate or whatever?

[SteveG_AudioMasters_]

In Multitrack, you can't extend a file beyond its recorded length - you'd need to extend it in Waveform view by adding silence, or whatever first.