Qrew LegendKanban Reports can do the vertical sort either on any field or else by enabling manually sort for the vertical columns. You can also the color the boxes so that is all pretty straight forward and it sounds like you know that already.
The drag and drop across columns only sets the value of a multiple choice field with no more than 15 choice including blank.
Your reference to Custom Data Rules confuses me as those can only ensure data integrity and blocking the save (including a Kanban drag and drop) if the rules are not met.
If you want the ability to drag the small projects, then that means that the choices for the columns - say if they were called [Status], needs to be a simple multiple choice field.
So if you want the Large Projects to auto calculate a status, then you will need to use form rules or Pipelines to set the value for the [Status] to be say equal to the value in the (formula text) field [Status Calculated for Large Projects].
The challenge though will be how to prevent users from dragging a Large project to a new status. I can't think of how to do that right now.
Qrew LegendI think if you could set the status for Large projects based on a form rule, then you can have a Custom Data rule to put up an error message when the Project is Large and status is not equal to the [[Status Calculated for Large Projects]. That will prevent a drag and drop for a Large Project.
