Hello,
My name is Sergey. I am Freelancer from Saint Petersburg, Russia.
I can help you as a WordPress programmer. Yes, I know Memberpress and Learndash.
In short words you want to be able to import one complex CSV file instead of multiple CSV files with the same users.
Please, can you show me this complex CSV file to analyze what data(columns) you want to import.
"name, email, password, membership id" - I understand. What "etc" means in your description?
I plan to form my work as separate WordPress plugin, I don't plan to modify WP core files.
2000+ successfully completed projects, including 200+ WP projects, speak for me. Links and reviews from my past clients available in my profile.
I am an individual, I am not a company in any meaning.
I need FTP access to start my work. And login/password into "wp-admin" Dashboard.
I can communicate via Freelancer.com.
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Sergey aka Takereal