The HELM project has developed a range of opensource tools which demonstrate what can be done with the notation.
HELM Web editor
Enables the user to create HELM strings by dragging and dropping monomers onto a sketchpad. Can interpret HELM strings or single letter sequences of natural monomers.
HELM Antibody Editor (HAbE)
Originally developed by Roche for internal use, they kindly open-sourced it for the community in 2018.
The antibody editor uses a Blast search to identify domains. The editor displays the domains and can manipulate the structures, creating Cys-Cys bonds and make other edits very flexibly due to the underlying HELM notation.
A Java-based toolkit that creates webservices that can be accessed by third party tools.
In 2017/18 Eva Bültel (Hamburg University supervised by quattro research) wrote her masters thesis on searching structures encoded in HELM.
The tools have now been open sourced and are available to the public.