Describe the knowledge and its acquisition with records that prove involvement, not content: version logs showing her authorship, change notices, commissioning reports, training materials and a manager's declaration. Confidential technical content can be summarized or redacted while the metadata stays intact.
Prove authorship and depth, not the code itself
Hypothetical example: a Haldimand County equipment maker is reluctant to put its controls source code and elevator design tables into a government filing. It does not need to. What the petition must establish is that the designer has specialized knowledge, how she acquired it and how the U.S.
assignment will use it. Export the firmware repository history with her name against releases, dates and one-line descriptions; attach engineering change notices she signed; include commissioning reports from installations she led; add the agenda and attendance for internal training sessions she delivered. Have the engineering manager sign a declaration explaining, in plain language, why the knowledge is uncommon and what would happen if a technician without it attempted a commissioning.
Redact proprietary values in tables but leave headings and dates visible. If USCIS issues a request for evidence, respond with more of the same kind of record rather than with the code. The strength of the file comes from a consistent, dated trail, not from disclosure.