The official route states that supporting documents are submitted with Form I-140G through the portal once USCIS provides instructions. Rather than inventing a checklist of mandatory items, assemble what genuinely evidences your own history: account statements, contracts, corporate filings, tax returns, and correspondence. Follow the actual instructions when they arrive.
Organise by story, not by folder
Sort material by the events it proves rather than by the bank that issued it. One transaction may draw on a contract from one country, a payment record from another, and a tax filing from a third; keeping them together makes the connection visible. Label each item with a date, an amount, and the event it supports.
A short index at the front saves a reviewer from guessing what an unfamiliar statement represents. Add one element to that index that a multi-country file particularly needs: a note of what each document is called and what it is, because a record perfectly familiar in the country that issued it can be unrecognisable elsewhere. A statement of account, a notarised declaration, a tax certificate, a company extract — each has a local name and a local function, and a single line explaining what a document does prevents a reviewer from having to infer it.
Add the language and whether a certified translation is attached. Hypothetical example: a file contains three documents whose titles translate literally into something meaningless, and one explanatory line per document, written by the person who obtained it, removes the largest single source of confusion in the whole set.