The "select all" of checkbox in grid does not select records that are not yet loaded in the form, how to be able to select all records?

Hi,

When I try to select all records in the grid for a custom form, it only selects records that are currently loaded and not the total number of records in the grid.

For example, I select all the records loaded, when I scroll up / down to load the other records, those other records are not selected.

The custom form has a pattern of "Simple List". But since it is a custom form, are there any setup or properties I need to adjust for the form / grid to be able to fix this issue? Or if not, are there a code I can add to achieve this?

Thank you!