FEDataInsertor

FEDataInsertor is the list-concatenation node: two list inputs in, one combined list out. input and append, both *-typed, and the node returns their elements merged - input's items first, then append's. That's the entire behavior, and it's about as boring as a node can be, which is the point.

It exists because this pack (like a lot of ComfyUI utility packs) treats Python lists as a first-class thing you pass through the graph - batches of prompts, lists of images, stacks of config values - and lists come from split/parallel operations all the time. When you've generated two batches of strings and want one combined list for a batch sampler, or you're building a prompt list and want to add a few extra entries at the end, FEDataInsertor is the splice.

The naming is worth a second look so you don't get burned: despite the word "Insertor," it doesn't insert at a position - there's no index input. It appends. The source shows it does out.extend(input); out.extend(append), so if the order of your lists matters, put the list you want first in input. It also expects actual lists: the node declares INPUT_IS_LIST on both inputs, meaning it treats what arrives as a list of items. Feed it a single value that isn't list-typed and the wiring can get confused - this is the classic *-typed-node trap where ComfyUI won't tell you the shape is wrong, it just misbehaves.

The output is output, type *, declared as a list. Wire it into anything that eats a list: a batch generator, another insertor (they chain), a data packer, or a splitter like FEDataUnpacker if you want to reorder and rejoin.

Realistically you'll reach for this node a handful of times a month, and only in workflows that already speak the pack's list language. It's a glue node - you won't build anything around it, but when a workflow hands you two lists and asks for one, it's the fastest way to get there. No config, no dependencies beyond the pack, nothing to trip on as long as you remember it's append, not insert.