Multicheck checkbox

I hope you are talking about multiple choice option to check in checkbox field.

Replace the single empty string in choiceLabels with an array of labels for your checkbox options.
Update choiceValues to be an array with corresponding values for each label. These values can be any data type, not just boolean.

choiceLabels: { "Option 1", "Option 2", "Option 3" },
choiceValues: { 1, 2, 3 },

Hi Shubham Aware 

Actually i am trying to save the check box's for multiple row's in the given grid at the same point of time.

 om786  I have updated your code for your reference.

a!checkboxField(
  choiceLabels: { " " },
  choiceValues: { true },
  value: 
if(
fv!item['recordType!{ed28cd83-aecc-434c-ac3c-48f88d5ab332}.fields.{d4e78775-ad64-4f7a-9881-ff6dac1ec243}'],
true,
null
),
  saveInto: 
  a!save(
    fv!item['recordType!{ed28cd83-aecc-434c-ac3c-48f88d5ab332}.fields.{d4e78775-ad64-4f7a-9881-ff6dac1ec243}'],
    if(isnull(save!value), false, true)
    ),
  align: "CENTER"
), 

You can refer this below checkbox code for your reference.
Let me know if you still have any question

a!localVariables(
  local!items: {
    a!map(id: 1, summary: "Item 1", primary:true,qty: 1, unitPrice: 10, dept: "Sales",   due: today() + 10),
    a!map(id: 2, summary: "Item 2", primary:false, qty: 2, unitPrice: 20, dept: "Finance", due: today() + 20),
    a!map(id: 3, summary: "Item 3", primary:true, qty: 3, unitPrice: 30, dept: "Sales",   due: today() + 30)
  },
  a!formLayout(
    contents: {
      a!gridLayout(
        headerCells: {
          a!gridLayoutHeaderCell(label: "Summary"),
          a!gridLayoutHeaderCell(label: "Qty", align: "RIGHT"),
          a!gridLayoutHeaderCell(label: "Primary", align: "RIGHT"),
          a!gridLayoutHeaderCell(label: "U/P", align: "RIGHT"),
          a!gridLayoutHeaderCell(label: "Amount", align: "RIGHT"),
          a!gridLayoutHeaderCell(label: "Department"),
          a!gridLayoutHeaderCell(label: "Due", align: "RIGHT"),
          a!gridLayoutHeaderCell(label: "Decision"),
          a!gridLayoutHeaderCell(label: "Reason")
        },
        columnConfigs: {
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 5),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE"),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE"),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE"),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 2),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 3),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 3),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 3),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 3)
        },
        rows: a!forEach(
          items:local!items,
          expression:{
            a!gridRowLayout(
              id: fv!index,
              contents: {
                a!textField(
                  /* Labels are not visible in grid cells but are necessary to meet accessibility requirements */
                  label: "summary " & fv!index,
                  value: fv!item.summary,
                  readOnly: true
                ),
                a!integerField(
                  label: "qty " & fv!index,
                  value: fv!item.qty,
                  readOnly: true,
                  align: "RIGHT"
                ),
                a!checkboxField(
                  choiceLabels: {""},
                  choiceValues: {true},
                  /* If fv!item.primary is false, set the value to null so that the checkbox is unchecked        */
                  value: if(fv!item.primary, true, null),
                   /*We want to save a false value when the checkbox  is unchecked, so we need to check whether       
                   save!value is null and update the variable if so */
                  saveInto: a!save(
                    fv!item.primary,
                    if(isnull(save!value), false, true)
                  ),
                  required: true,
                  requiredMessage: "You must check this box!"
                ),
                a!floatingPointField(
                  label: "unitPrice " & fv!index,
                  value: fv!item.unitPrice,
                  readOnly: true,
                  align: "RIGHT"
                ),
                a!textField(
                  label: "amount " & fv!index,
                  value: if(
                    or(isnull(fv!item.qty), isnull(fv!item.unitPrice)),
                    null,
                    a!currency(
                      isoCode: "USD",
                      value: fv!item.qty * fv!item.unitPrice
                    )
                  ),
                  readOnly: true,
                  align: "RIGHT"
                ),
                a!dropdownField(
                  label: "dept " & fv!index,
                  choiceLabels: {"Finance", "Sales"},
                  placeholder: "--Select-- ",
                  choiceValues: {"Finance", "Sales"},
                  value: fv!item.dept,
                  disabled: true
                ),
                a!dateField(
                  label: "due " & fv!index,
                  value: fv!item.due,
                  readOnly: true,
                  align: "RIGHT"
                ),
                a!dropdownField(
                  label: "decision " & fv!index,
                  choiceLabels: {"Approve", "Reject", "Need More Info"},
                  placeholder: "--Select-- ",
                  choiceValues: {"Approve", "Reject", "Need More Info"},
                  value: fv!item.decision,
                  saveInto: fv!item.decision,
                  required: true
                ),
                a!textField(
                  label: "reason" & fv!index,
                  value: fv!item.reason,
                  saveInto: fv!item.reason,
                  required: and(
                    not(isnull(fv!item.decision)),
                    fv!item.decision <> "Approve"
                  ),
                  requiredMessage: "A reason is required for items that are not approved"
                )
              }
            )
          }
        )
      )
    }
  )
)

thanks so much Shubham Aware 

issue resolved now...