Combo Boxes Passing Selections to Other Dashboards

 it may help to use the same bound parameter across multiple comboboxes that need to display the same default choice, or just use the same combobox with its bound parameter.  You can also pass the value of the combobox bound parameter to the Dashboard Extender rule by assigning it to an argument {DBExtenderRule}{ComboboxFunction}{combo1Val=|!pm_combo1val!|}.  Then assign it to another parameter in the rule:

Dim taskResult As XFSelectionChangedTaskResult = New XFSelectionChangedTaskResult() With {
    .IsOK = True,
    .ShowMessageBox = False,
    .Message = "",
    .ChangeSelectionChangedUIActionInDashboard = False,
    .ChangeSelectionChangedNavigationInDashboard = False,
    .ChangeCustomSubstVarsInDashboard = true,
    .ChangeCustomSubstVarsInLaunchedDashboard = False
}

taskResult.ModifiedCustomSubvars("combo2Val) = combo1Val

Return taskResult

In addition to Robb's comment, you could also use the extender rule to set the value to a literal value parameter that can be read by the new dashboard

Hey Michel,  Wouldn't setting a Literal Parameter set the default for the combobox its bound to for all users?  I think Andy wants this for each user.

I was running into a similar issue with selecting multiple items in a combo box and passing it in to the dashboard extender rule. Only the first item selected would write to the error log. I found a separate post on here (https://community.onestreamsoftware.com/t5/Rules/When-selecting-multiple-items-in-the-list-box-only-the-first-one/m-p/19788) that recommended the use of [ ] when passing in the named value pair into the dashboard extender rule and this appears to be working as expected! 

Since you have a load event, why not store this as session info, when the other dashboard opens get the session info, and set the parameter with this value?