Subfetish editor
The subfetish editor is a really weird feature of f-list, but it's useful once you figure it out. It saves a lot of space in case you want to fill your kink list with custom kinks, as you can see in the demonstrative images. A word of warning, though: you cannot insert custom kinks into subfetish collapses [yet; the feature is planned for the future, let's see where it goes].
Subfetish headers are just custom kinks. So before you set up anything, you'll want to create some custom kinks that you will later turn into collapses.
There are several ways to sort these collapses, do it any way you like. It might take some playing with first before you figure out exactly how you want to do it, and a trick I prefer using is to make a non-public profile specifically for fetish editing... so you can copy the kinks from your extra profile to your in-use one after you finish the whole thing.
Once you're ready, go back into the character editor, and you'll find the subfetish editor in the Kinks section. It takes you to a... very interesting page that will open itself in a new window. When you first look at it, you probably want to just leave, or at least, that's what I did the first time I saw this. I just screamed "NOPE NOPE NOPE NOPE NOPE" and then forgot where the subfetish editor was located for like 3 years. That's why I'm writing this to begin with. Nobody will suffer.
Anyway, to begin, pick a kink group. Let's go with "general". You may want to reference this list to help locate certain kinks.
Let's say my character is scared of contortionists, they freak her out, sure. To do that, after clicking "general" where the "flexibility/contortionism" kink is located, click on the custom "fears" kink next so that it's selected, then press the "add kink >" button. You'll get this.
If you've already sorted several kinks, they'll be highlighted on the list in a colour representing what list you have it sorted onto. You can still insert these into a collapse and all will work just fine, even if the custom kink you inserted into the subfetish was sorted somewhere else. Its new location will be under your subfetish heading. This is what it might look like:
Go ahead and save once you're done, close the subfetish editor window, and go back to your character edit page. Make sure you save your changes there, too.
Here's what it looks like on a profile, now. I moved "dating", which was sorted into the "maybe" list, under "fears" for demonstrative purposes. Unsorted kinks remain on their lists outside of the collapse, which is useful if you want to draw attention to them or only display non-sexual kinks on the list while sexual ones are displayed under collapses. There's a lot of techniques you can use to make your character profiles suit your needs and this is a useful tool that gives the site that much more versatility. Hope you enjoyed the guide and that it was comprehensive enough!