bank wants an organigram of my holding and subsidiaries how do I make that

Group structure: Chamber of Commerce extract plus your own diagram

The bank is actually asking two things at once: the formal legal structure, and how it works in practice. For the first part, there is a reliable source: the Business Register. For the second part, you must draw it yourself, because an organizational chart as such is not described anywhere as a mandatory document.

The formal side comes from the Chamber of Commerce extract of the holding company and of each subsidiary. It shows who the director is, who the shareholder is, and whether a parent relationship is registered. For the question under what registration number is the company registered the Chamber of Commerce number of each entity separately is sufficient; place those numbers side by side and the legal lines often become visible without you needing to draw anything. The organizational chart itself — the drawing with boxes and arrows — is a summary you make alongside it: holding at the top, subsidiaries below, shareholding percentages next to them, and where relevant a separate line for an operating company that itself has a subsidiary. Banks often also want to see which entity takes responsibility for which part of annual turnover and which part of the employees so a table next to the diagram helps. If you have an entity that has just been set up or spun off and that has no figures yet, state that explicitly instead of filling in an estimate.

No statutory format, but a statutory source

There is no prescribed form for an organizational chart; the Business Register Act 2007 does require registration of the basic data per undertaking — name, legal form, directors, places of business — and that is the source from which you build the diagram. Other frameworks in this overview, such as the VSME-basic module or the NIS2 directive, concern sustainability or cyber reporting and say nothing about group structure; do not use them therefore as support for this answer.