Text editors/IDEs have simple autocomplete and the ability to do some expansion, e.g. a for loop with placeholders to fill in. Those work and are still useful.
JetBrains also has local line-based LLM models for various languages.
With the LLM-based autocomplete it a) generally autocompletes more code at once, and b) will often pick up on patterns in the existing code. E.g. if you have a similar method, list of print/string buffer write statements, or other repetitive code in the file it will often use that as a model for the generated code.
That sure sounds like you're describing customizable snippets, which AFAIK every major editor supports?
The JetBrains local autocomplete is hilarious but occasionally useful. I find it really hit and miss in terms of when it will decide to autocomplete and whether it will exhastively complete all elements, miss some out or get itself into a loop over several.