The on-site trainer tells you that the sample prompts for testing each epoch is an optional thing, but this is a terrible idea. It never clearly explained what it meant and I never used it so I was curious what it would if left blank. I was training a 2.0 model and didn't really need to check anything in particular, so I left #2 and #3 blank.
Big mistake!
What it automatically fills these in with is just a random selection of tags from your training data, and you don't get a chance to say no. The tag selection appears to be inverse to how much they're actually used, using the least used tags from your TD instead of the most used. Neither of the two autogenerated prompts contained the trigger or the character's physical identity, but they both contained multiple tags that were only used once, some which aren't even booru/pony recognized tags, and contradictory tags ("2girls, 1girl", multiple poses that can't be combined). It also contained tags that could inadvertently produce sexual images (were the results not such a contradictory mess). At best this is useless, but it might even produce something horrible instead of just nonsense. It's so bad I'd actually suggest disabling this auto prompt generation "feature". It would be far better to force users to pick a prompt and just give some format suggestions per resource type (just simple skeletons like a character lora might suggest "score_8, score_8_up, score_7_up, [artstyle], [character tags], full body, looking at viewer, V, outdoors, forest, grass" with different variants for front/side/back)