Can you change the null drop threshold for a single column?

Answer:

No, because the null drop threshold is a global setting, changing it will impact the entire model.

However, there is a workaround - you can perform a per column intervention on the column that you want the model to try but is too null and is being automatically dropped. Find the column in the ‘Add Column Intervention’ dropdown and click the ‘+’ and make the column not droppable in the ‘Droppable’ dropdown menu. This will tell One AI to still try this column in the in model despite it violating a global setting. If the column contributes to better performance and fit for the model, it will be selected. 

Alternatively, you can perform a null-filling per column invention so that the column is not dropped due to being too null. There are several strategies available, including mean, median, model, bfill, ffill, and custom.