Incorrect text when talking with NPC Vugma (Harvesting Supply Vendor) in Martok - /loc 45582, 43220, 7014 in Martok (-20, 13)
You start with the option of selecting a Primary and/or Secondary Harvesting Skill.
Even if you have already selected/confirmed a primary skill through previous dialogue, if you choose "I want to select a new secondary harvesting skill," and then choose either option (i.e.quarrying, skinning), the bottom option of the 3rd dialogue states "What were the other options for my primary skill?" The problem being the confusion of it asking for other 'primary' skill options while you're trying to choose secondary.
If you select that option, it will take you back to choosing a different skill. If you choose one and then proceed to the 3rd dialogue again, and choose a skill, it DOES, indeed, set it as a secondary.
I hope this helps. If you need more info, hit me up on Discord!