I want to know how to switch tables on the dashboard

Is there a way to change only the referenced table without changing the line graph display settings?

Sadly not. I have a customer where I have to replicate all the charts.
In theory, you could edit the Metabase database to use a different table, but it’s far from trivial.
Alternatively, you could either use a query or a view for the question.

Thank you for your reply.
As I thought.

Load a CSV file, created once a day, into daily database tables.
By filtering by day, I wanted to see multiple questions (multiple database tables) in one graph on one dashboard.

Create a UNION view of the tables with an extra column for the date of the import. Then group on the date.
Depends upon your database.
If MS SQL Server, you could have the import done automatically and use current date or filename as the date column. Can probably do on most others too.

Thank you.
I will try out.