Uxerkit is a free Sketch template for creating user flows in minutes. It is a symbol library of responsive UX flow components using color variables, and resizing features to enable the symbol to stretch and scale to suit your project.
View a video demo: https://youtu.be/LsqfkPGElmc
UX arrow symbols include: Straight, Diagonal, Curve, Hook, U-Turn and Snake with a choice of multiple start and end symbols. Each symbol contains multiple label options which can be turned on and off via the symbol overrides in the inspector panel.
This incredible resource is released with the “pay what you want” model ($0, or more if you want to donate some bucks to the author).