We are in pega 24.1 version and trying add the Pega OOTB multi select option from Grid layout properties
@SanthoshL2561 Please can you clarify your configuration and the symptoms you are experiencing? The issue described in the support document Missing Select All Checkbox in Data Reference Multi-select is specific for 24.2 users, and relates to the check box missing. (The “Select all” checkbox is displayed if the selectionCountThreshold >= filteredListCount).
There are some limitations to the use of the MultiSelect grid with Data Reference. You should not be using any Declare Index on Copy type autopopulate property context. In the next available 24.1 Patch there is a fix which will disable Autopopulates in RecalculateAndSave activity before calling the save operation.
If your issue is different, then I would suggest that you log a support ticket via the MSP. If you decide to log a ticket, please provide the INC reference here in a reply.