Restrict SharePoint folder on individual level?

Michael_Paolantonio Regardless of the solution you choose to build this functionality, it will involve a lot of rights administration. Setting individual rights on SharePoint folders or (in the worst case) on individual elements quickly becomes a nightmare if you want a good overview of who has access to what. Without knowing enough about the concrete needs of your client, I personally would rather base the solution on Microsoft Teams and perhaps consider each Case as its own Team and therefore establish a Team per Case. When a Case is closed, you can also easily archive it. Yes, there will be many Teams, but with a few small fixed routines, it will be much easier to have an overview of and administer the members than trying to do the same job in a SharePoint site with unique rights at different levels.

If your client is not yet using Microsoft Teams, this might be a good opportunity to show them how this can help them. If, as expected, it should prove impossible to get them over on Teams, it is better to have a SharePoint Modern Team Site per Case in order to have a better overview of members/rights even then. Then you are also better prepared to be able to create Teams for the sites in the future.

Regards, Magnus