How to save ListBox Multiselect to Registry

You could read them from the spreadsheet in the Userform_Initialize procedure.

Example

Private Sub UserForm_Initialize()
    Dim i As Long
    For i = 1 To 12
        Me.Controls("Listbox" & i).Value = Sheets("Sheet1").Cells(1, i).Value
    Next i
End Sub

You could store them as a customer property.

Each listbox name would be use to store a string of CSV for later use.

Each CSV would represent the selected value in the listbox.

If you had a list of ten in Listbox1 and 1,3 7 items are selected, this would generate a CSV like:

Listbox1,1,3,7

which you can parse later with the Split function.

Private Sub cmdSave_Click()
Dim Ctrl As Control
Dim A As Long
Dim LBAry As String

For Each Ctrl In Me.Controls
    Select Case Ctrl.Name
    Case "ListBox"
        LBAry = Ctrl.Name & ","
        For A = 0 To Ctrl.ListCount - 1
            If Me.Ctrl.Selected(A) Then
                LBAry = LBAry & A & ","
            End If
        Next
       'Strip off trailing comma.
        LBAry = Left(LBAry, Len(LBAry) - 1)
        StoreVariable Ctrl.Name, LBAry
    End Select
Next

End Sub

Sub StoreVariable(Varname As String, VarValue As String)
'http://www.vbaexpress.com/kb/getarticle.php?kb_id=677
 '   ============================================
 '   Save a value in CustomDocumentProperties
 '   ============================================
 '   If the name doesn't exist, we create it and set the initial value to 1
On Error Resume Next
Dim cstmDocProp As DocumentProperty
Set cstmDocProp = ThisWorkbook.CustomDocumentProperties(Varname)
 
If Err.Number > 0 Then
     
    ThisWorkbook.CustomDocumentProperties.Add _
    Name:=Varname, _
    LinkToContent:=False, _
    Type:=msoPropertyTypeNumber, _
    Value:=VarValue
     '   ========================================================================
     
Else
     
     '   ========================================================================
     '       if our name exists, we need to store the csv.
    ThisWorkbook.CustomDocumentProperties(Varname).Value = VarValue
     '   ========================================================================
     
End If
 
 '   Explicitly clear memory
Set cstmDocProp = Nothing
     

End Sub