Hello Sarm!
A as 'ODS_TYPE_BOOL' allocated variable is internal a long integer. Therefore it will be defined as Longinteger in SUD. Second: 'ODS_TYPE_BOOL' variables can not be set with the VBScript 'true' you have to use 1 instead. You have two 'bln_Test' variables in your script. Delete the 'Dim blnTest_'. VBScript variables will win in the script! In the SUD dialog the DIAdem variable with the same name is used.
This changes result in this modified script:
Option Explicit
Call OdsValAlloc("blnTest_","ODS_TYPE_BOOL")
blnTest_ = 1
MsgBox "blnTest_ = " & (blnTest_ <> 0)
Call SudDlgShow("Dlg1", "blnTest.sud")
MsgBox "blnTest_ = " & (blnTest_ <> 0)
Call OdsValFree("blnTest_")
Matthias