I was in the same boat as you the first time I levelled up. I got through my radicals, and moved onto kanji, which made sense. Then I finished my kanji, did my reviews, and then expected to move onto vocab, but while I did, the dashboard changed and it confused me! I was left wondering where I was supposed to go - was it supposed to work on vocab? Move onto the radicals and kanji for level 2? I went and looked back into the detail of how Wanikani works, especially using the link that @seanblue gave you. Then it made more sense.
I can see where you’re coming from, in that it probably would be nice to have a visual representation of the vocab you’re currently learning, but agree with the other comments you’ve had here. But looking at just how much vocab is in some of the levels, it really would be so cluttered on the dashboard that it probably wouldn’t be that helpful.
There are some userscripts that I use to give me some visual representation of my progress. The main one is [Userscript] Dashboard Level Progress Detail. update to broken script, which shows me a progress bar for all of the levels I’m currently working on.
I have another userscript installed that shows me the SRS level of the kanji and vocab when I’m on the actual kanji/vocab pages, not the dashboard. [Is there a script that shows previous level progress?]
They might help scratch your itch a bit.