By default, Odoo does not support selecting multiple records at once in the Kanban view to move them to another stage simultaneously. 
To achieve this functionality, you would typically need to use the list view.

Hi Maurice,

this will be a feature of the new minor-release Odoo 18.2, which will be available for Odoo Online users. There is a high chance that it will be also a feature for Odoo 19 I guess.

Regards,

Chris Dominiak (Intero Technologies GmbH)