The company's own procedures with authorship and version history, training records showing who has been taught them, project documents naming the engineer's role, and a petitioner letter explaining why the U.S. affiliate needs that knowledge.
Documents that predate the petition carry the weight
Hypothetical example: a Mission berry processor assembles its L-1B file and discovers the only description of the engineer's knowledge is a paragraph written for the petition. That paragraph will be read as advocacy. The stronger evidence is what already existed: the standard operating procedures with the engineer named as author or reviser, the change log showing her revisions, the internal training matrix listing which staff have been certified on the procedure, performance reviews mentioning the work, and any group-wide communications adopting her method.
Add the U.S. affiliate's project plan showing where the knowledge will be applied, the corporate ownership documents, and payroll for the qualifying year. A letter from the petitioner ties it together, but it should cite the underlying records rather than replace them.
Translate anything not in English with a certified translation. Hypothetical example: A specialty-coffee roaster wants to send its quality specialist to a U.S. affiliate and relies on a new statement that she knows its roast-profile system.
The first review should seek records made before the petition: version-controlled profiles, access logs, training agendas, quality reports and messages assigning her that work. Those records show both the knowledge and its connection to the business. Combine them with corporate ownership proof, payroll for the qualifying year and a U.S.
duty description. If the employer cannot identify what the person will apply in the new role, the paperwork describes a capable employee, not necessarily an L-1B transferee.