I'm responding to this as I encountered similar problem recently and thought it would be useful for other folks too!
steps used to resolve
1. activate Tab 1 and use send keys event "<{CTRL}{TAB}"
2. Then activate Tab 2 and perform actions required
3. Use send keys event "<CTRL}{SHIFT}{TAB}" to switch back to previous left tab
Otherwise (most suitable option)
1. Use Navigate stage and use Parent element -> Navigate action -> Address with value of second tab URL
This will navigate in the same tab and you may continue spying or working with the elements.
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Sahana Mohan
Solution Designer
Blueprism
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Sahana Mohan
Lead Software Engineer
SS&C Blue Prism