Confirmation GUI

Hmm, we hover over the emerald block and it says "Confirm. Rankup to member", but it doesn't say anything about needing the xp levels. Let's do something about that! Just like with requirements-not-met: <text>, we can use Option 1 or Option 2 to remedy the confirmation gui:. For this example we'll start with Option 2.
Go back to your locale/ file and find the gui: section under rankup:.
Confirm. Rankup to member.

The gui: settings used in the image above:

      material: EMERALD_BLOCK
      # index can be separated by spaces to show in multiple groups
      # for example: 0-3 9-12 18-21
      # you can also just use a single number instead of a range.
      index: 0-3
      name: '&a&lConfirm'
      # lore is optional
      lore: '&6Rankup to &b{{ next.rank }}'
      material: REDSTONE_BLOCK
      index: 6-8
      name: '§c§lCancel'
      # since all slots are used by , no fill is visible
      name: ' '

The index starts at 0 and goes to 8, as you can see in the image below.
index for ease of access
To change the lore on the items in the UI to tell players how many xp levels they need for this rankup specifically, we'll use Option 1. We could use Option 2 to edit the UI for all rankup steps in the locale, but subsequent ranks may not utilize the same requirements which would display incorrect text in the lore like Costs {rank.requirement('xp-level').total | simple }} xp levels., similar to You need {{ rank.requirement('money').total | money }} money to rankup..

Modify your rankups.yml like so:

  rank: 'default'
  next: 'member'
    - xp-level 5
    requirements-not-met: "&cYou have {{ rank.requirement('xp-level').progress }}, and need {{ rank.requirement('xp-level').total }} xp levels to rankup!"
        material: EMERALD_BLOCK
        index: 0-3
        name: '&a&lConfirm'
        lore: |-
          &6Rankup to &b{{ next.rank }}
          &eCosts {{ rank.requirement('xp-level').total | simple}} xp levels.
      #since we don't need to change the cancel or fill sections, we don't need them in the rankups.yml
        #material: REDSTONE_BLOCK
        #index: 5-8
        #name: '§c§lCancel'  # section sign color codes are also outdated
        #name: ' '
        #material: BLACK_STAINED_GLASS_PANE

NOTE: the way lore is written has changed! Since we wanted 2 lines instead of one, we used multiline formatting and properly indented.

NOTE: the filter simple applied to the placeholder makes it so the placeholder outputs whole, unformatted numbers. otherwise it would output 5.0.

Save and reload the plugin, then try /rankup again.

Now showing how much it costs
This is much better!
That covers the basics of creating Rankup steps. For more information, look at the comments in the configuration files, check out the Advanced Example or look at other pages here on the wiki!