Prior to this latest patch, you were unable to see what the next rank objectives were because you could not look at them in the list. However, if you went to some other source like https://d3resource.com/index.php and used his Journey Tracker, then you could complete the higher chapter objectives, and if you omitted, for example, the Set Dungeon mastery for Slayer and Champion, and using the Journey Tracker completed all higher objectives right up to Guardian, then regardless if the drop-down list would display any of the higher chapters, the instant you mastered that Set Dungeon, you would instantly complete all Season Journey chapters right up to Guardian, it would show you that you did, as amply demonstrated by the various screenshots provided, and you would receive all rewards for all chapters for the entire Season Journey.
I really wish they would add a new objective to each level that gets a check when the prior level is complete. This “bug” comes up far too often ever since they changed the ability to view later chapters even though you haven’t completed what your on.
Example:
Champion Tier:
{ } Complete All Objectives of Slayer
Destroyer Tier:
{ } Complete All Objectives of Champion
etc.
Other then that, you ONLY need to Enlist from Chapter 4 to Slayer. That is the ONLY time you need to ENLIST. It is not required to enlist after that to receive any rewards or complete a tier. As stated above, I have also put off the set dungeon to the end and got awarded basically all tiers as soon as I finished it.
The other thing to point out is that enlisting only is there to see the objectives for the next chapter for your benefit. It has nothing to do with completing the season journey. You can complete the entire journey without once opening it. You can rely entirely on the 3rd party season tracker and you will still get all the rewards.
Fixed that link for you. 
