In MJML seems there is no way to nest mj-column's, So how do you create nested columns?
This is what I'm trying to build:
I tried using mj-section and mj-wrapper too but seems none of these tags can be nested.
You're right about not nesting MJML mj-columns.
This design is tough to make responsive.
You'll want to use good old HTML. Maybe you'll want to use the long-traditional embedded tables so often used in email HTML.
In MJML, you can use raw HTML in mj-raw, mj-table, and mj-text. Among those, maybe mj-table is your best choice; it also substitutes for the HTML tag <table></table>.
You can equally do it in the others if you prefer; they'd need that tag.
BTW, lots of questions just like this get prompt answers at https://slack.mjml.io/.