The correct syntax is:

Add Data Menu!Record Commands!Delete Record (F3)
Search Update Menu!Record Commands!Delete Record (F3)
Change shown in bold
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var vNav as Int
If @Update
{
vNav = @SelectTreeItem("Search Update Menu!Record Commands!Delete Record (F3)")
}
If @Add
{
vNav = @SelectTreeItem("Add Data Menu!Record Commands!Delete Record (F3)")
}
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Version 2 now has a great Menu Tree Picker so you don't have to remember.

In the Program Editor, right click in center, select List Browser.  Now click on Switch 3 times to see the  Menu Tree Items.  Select the one you want, and click on Insert

The list browser defaults to SBasic Commands, and subsequent clicks show Element Names, Font Names, and Menu Tree Items, and continues to cycle.
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Other things to consider if still not working:

1.  Is programming in the OnElementEntry section for the button?

2.  Is @NotifyForm() not set to 4 ?.  Value of 4 prevents deletion.