As per this quote from the developer:
Only two top skills are displayed, but there can be more of them.
The reasoning for only displaying two was also mentioned in that same thread, higher up:
Census will be too overburden on a higher population otherwise.
Looking at the code, the skills' information is as follows:
- Dabbling - No XP required - No bonus
- Novice - 100 XP required - 1.25% Bonus
- Adequate - 500 XP required - 2.5% Bonus
- Competent - 1200 XP required - 4.5% Bonus
- Skilled - 2500 XP required - 7.5% Bonus
- Proficient - 5000 XP required - 12.5% Bonus
- Master - 9000 XP required - 18.75% Bonus
Thus, a kitten who is splitting their time up between two jobs about evenly is going to still be under proficient when a kitten who'd focused on the same job all the time has made master. You're probably better off letting a small number of kittens focus on Farming continuously through the year; you won't get much benefit right away, but when they finally do make master, they'll be able to feed more kittens, especially with the upgrade later on that doubles how much bonus all skills give.
Even worse, any kitten who has skill in a job they're not currently doing, will slowly (very slowly) lose experience in that job. The effect of this is minor (five thousandths of an XP per second), but if you're idling for long stretches, it can stall progress if you're trying to teach a kitten two jobs.
In the end, though, it doesn't matter too much what you do this early in the game. Getting to master-level kittens takes a while, and swapping your kittens around won't stop them from making master in their jobs eventually; just slows it a little. Plus, once you get more Pastures, and the Hoe upgrades to your farmers, even a small handful of Dabbling farmers will be enough to feed a fairly large population through cold winters.
Best Answer
As a work-around you can temporarily "unassign job" the ones you can see, then switch the job selection menu away and back to see some more. With 34, you'll have to unassign at least 24 in total to see them all.
You can, at least, keep clicking promote on each worker until it stops helping.
Then reassign everycat and carry on.