Starting with the release of Strategy ONE (March 2024), dossiers are also known as dashboards.
SYMPTOM:
Notification “The dossier will attempt to display more than 250 columns. This can affect performance and stability.” Occurs when manipulating Dossier and trying to drop an attribute in columns even if the final column number is lower than 250 in Strategy 10.4 or above.
Follow below steps to reproduce the issue in Tutorial project:
1. Create a report with attribute Quarter, Month and metric Cost.
2. Create a dossier and put Month in Columns and Cost in Metrics.
Note that there are 36 columns.
3. Drag and drop Quarter to Columns. Below Notification message will occur:

The dossier will attempt to display more than 250 columns. This can affect performance and stability.

The attribute Customer(10000) has too many elements. This action may impact dossier performance.