Column we can surely add, please follow below step:
1) Open that button record on "sys_declarative_action_assignment" table.
2) Click on advanced view
3) Go to the Action Attribute section
4) In Payload Map select Column and there are already column name, you can add extra column name. Please check once below image for reference.
It is not possible to increase size of window popup. It came OOB.
Please check first approach and let me know if it helpful or not.
