hm...

This looks like the best basis to work with. But I can't follow the way the formulas work.

Would I need to adjust the helper columns in data manually?
The data that will be copied there never changes when it comes to columns, but the rows can vary wildly to up to 12.000.

I would use the "Report" sheet as the basis to create the sheet where the "feedback" and "progress" can be added as that is the most important part about the entire file.

In that case I only need to generate multiple report sheets for each "age group" (ages 10080 - 20160, 20161 - 30240, 30241 - 43200, 43201 - 64800, above 64800).
This sheet would only need to contain the "ID", as it only serves as a helping sheet to filter data by "age".

The only formula I have a tenuous grasp on is the one in RepRow, but nStartAge and nEndAge throws me off. I know that it refers to the values in "Report", but I don't know how.
I need to understand it, so I can create the sheets where users can enter their feedback and progress.

Thank you fjns and ArviLaanemets for the great work!