Mass Update For Custom is not possible ,hence we can update forms through CSV Import
Here are the steps for updating forms through CSV import:
1.Navigate to Import/Export: Go to Setup -> Import/Export -> Import CSV Records.
2.Select Transaction: Choose the appropriate transaction type.
3.Upload the CSV File: Upload the CSV file containing the updates.
4.Choose Update Option: Select “Update” for the operation type.
5.Use Advanced Features: In the advanced features, select the corresponding form you wish to update.
6.Update Internal ID: Ensure the CSV file includes the internal IDs of the records you want to update.
7.Run the Import: Provide an import map name, description, and ID, then click “Run”.