Filtered data in Excel online are visible for all users

Haytham AmairahI agree it is for collaboration, but I think you have missed the fact that there are different ways to collaborate. It might make sense for two people to edit the one record/row/column/cell sometimes, but in my experience the majority of Excel files edited by multiple users via SharePoint or o365 are edited in a way where different people edit different rows at the same time. It seems to be more the case that Excel files are created for multiple people to contribute such that it is the sum of edits from all users, not a collection of single edits that have each been agreed on by two or more people. Do you follow? E.g. you add data to rows 1,3,4,6,9, I add data to rows 2,5,7,8,10 etc...but we do not edit the SAME rows or cells...one file, multiple rows/cells, each row/cell edited by ONE person, not multiple people.

Having the ability to only locally filter an individual user's view would most definitely be welcome and useful, and I would bet money on that kind of editing (different people editing different rows/cells rather than collaboratively editing cells together) being what really happens for most of these shared Excel files.