Open NIGTC: Revelation.
Open the Table of Contents panel.
Expand sections of the TOC until you find some of the really long sub-section headings (e.g. "John is Commissioned to Write to the Churches Because the Initial Vision He Receives Demonstrates that the Saints’ Confidence is Grounded in Christ’s Installation as Cosmic Judge, Priest, and Ruler of the Church as a Result of His Victory Over Death (1:12–20)" or "Christ Commends the Church in Pergamum for Its Persevering Witness in the Midst of Persecution, Condemns It for Its Permissive Spirit of Idolatrous Compromise, and Exhorts It to Overcome This in Order Not to Be Judged But to Inherit End-Time Fellowship and Identification With Christ (2:12–17)").
Hover your mouse over one of these long sub-section headings in the TOC, and you can't see the verse references in the pop-up window, because they come at the end of the heading. This makes it hard to navigate by way of the TOC to find a particular passage in Revelation.
I know it isn't Logos's fault that the author of this particular commentary has used such long heading titles (this is the only volume in the series I could find that had this problem). But couldn't you use a little editorial oversight and put the reference numbers for the subsections at the beginning of the headings like they are for the main section headings? At least in the TOC panel? (Though that latter might be hard to do if you don't do it in the heading itself since I'm getting the TOC panel gets the text from the heading as it appears in the body of the resource.)

UPDATE: I just realized that the illustration i showed has a different subsection heading selected than the one I hovered over so the red arrows are kind of misleading. That particular reference text is not being truncated from the end of that particular popup. But you still get the idea.