Maybe Glenn came up with the lick, but if that's the case, it would really surprise me if he's playing that lick and all of the guitar fills on the record simply because the tone/timing of the guitar sounds more similar to Don than Glenn to my ear. The tone of the guitar is also consistent from the chorus licks to the Felder part in the solo, but Glenn's part in the solo sounds a bit different tonally to me. Also, Don would play all of those fills and the lick live and sounded much the same as the record imo.
Of course, it's ultimately speculation on my part. Taking apart the arrangements and trying to determine how the instrumental/vocal parts are laid out is generally pretty instructive to me, so any info about who actually did what is always cool to learn.
To respond to I've always been a dreamer, what sets NKIT apart from earlier Eagles releases imo is the way it's laid out. There aren't many fills during the vocals, but they happen in the gaps between them. afaik that's a Felder tendency as Bernie tended to play fills a lot more frequently than Don in the early Eagles. Also, many of the chords use the open B and E strings and walk up and down to different chords using arpeggios. Signature Felder tendency to my ear; he did that all throughout his time with the Eagles and afterwards.
I'm willing to buy that JD or Glenn could have contributed a lot more to the arrangement than I'm aware of, but NKIT doesn't sound too much to my ear like the way Glenn arranged songs (it has some of his tendencies, but the structure is unlike his solo stuff imo).
Desperado had a fairly complex arrangement too, but it was played more chordally, and you didn't really see the same tendencies of very clear walkups, walkdowns, emphasis on suspended chords and open strings, etc. All that is how Don arranges songs, however.