Board owner & folder owner: Increasing a user's editing rights
By default, regular users (lacking any special privileges) and project managers only have access to the boards that were shared with them, or to those that they’ve created themselves.
A good way of allowing these users to edit a board, that was not created by themselves, is to make them a board owner. This will enable them to edit to the board’s settings, without you having to give them admin privileges.
The board owner access right can be assigned from a board’s share option.
Correspondingly, the same can be done for an entire folder of boards.
If you tend to create a folder for each project or area of work and this area has a dedicated user, it is recommended, that this person is made an owner of this folder. This allows them to edit the boards that were placed within it without having to get higher access privileges.
Note, that just sharing a folder with a project manager will only allow them to view and work on boards already present in this folder and to create their own boards. They will not be able to edit these board settings until they are made an owner of that folder.