I think one of the hardest types of light curves to classify in terms of variability as well as identifying transits in are the pulsating ones or pulsators as the Science Team has dubbed them. There are many types of pulsating stars but we’re referring to those where the star’s brightness is rapidly oscillating up and down over the 30 day period with many cycles in the span of 5 days
One example is SPH10074728:
You can see there’s a a discernible up-down (nearly vertical) changes in the star’s brightness. When classifying I would have said this was variable and selected the pulsating button or
I find these stars the hardest to identify transits in. For the example above, I would say there are no transits, and all those dips are due to the natural variability of the star. At least one of our current planet candidates is from a pulsator like this, so there can be transit signals in these light curves., They’re just a little harder to spot than the quiet curves. One thing to keep in mind when classifying that may help on these types of curves is that the dip from a transit typically lasts a few hours to ~10 hours, so if you see dips lasting days, those aren’t due to orbiting bodies. But go with your gut, if you think there’s a transit definitely mark it, if it’s real others will mark it too.