Starting with the release of Strategy ONE (March 2024), dossiers are also known as dashboards.
SYMPTOM:
When adding a reference line in a graph in Dossier 10.9, the following error occurs:

An error has occured We are sorry for the inconvenience. Please contact your administrator for help. Error: Object.keys : argument is not an Object

3. in the Format pane, select Reference lines, add any of the available and notice the error
CAUSE:
This is an identified issue with Strategy Web 10.9.
ACTION:
This issue has been addressed in Strategy 10.10. Upgrade to this version to take advantage of this fix.
WORKAROUND:
Use another browser than Internet Explorer.
Article Reference Number: KB440762