specific view mode for view duplicates

@matoeil, can you provide steps to reproduce, starting from install Drupal core?

Changes are made on on 11.x (our main development branch) first, and are then back ported as needed according to the Core change policies → .

Restoring template. The issue template is used to track progress and various tasks on an issue.

I’ve followed the steps to reproduce the issue as described, However, when duplicating block displays, changing the view mode for one block display will affect all duplicates. This is because view mode settings are shared across block duplicates by default in Drupal. This is the intended behavior, as view modes are part of the shared display configuration in Views, and they are not treated as independent settings per block display.
To achieve independent view mode settings for each block, it’s necessary to create separate block displays instead of duplicating the original block display. This allows each block to have its own configuration, including different view modes. solution could involve enhancing the Views UI to support independent configuration of view modes per duplicate.