Some columns in the two tabs are not similar, For sure there is one or two elements are unique find that unique and use check app state activity to check which tab you are in.
In Main Tab the UOM column, Request Date column are unique try to indicate the two of one in check app state and try.
Too Legacy to automate, here you would have to forget the best practices for automation, and you would have to use Get Text activity for a certain Idx, for example you can check with UOM header itself here.
IF you can see UOM Header then its on Main tab, else use a click activity or Shortcut to get to Main tab.
Its an oracle ebs screen…what do you want to verify…instead directly click on main always…
And after click…check the index properties…one of the property would be set to true or 1 once the required tab is selected
Another way is to perform a click visible text activity on the Request date …and it wpuld be successful only when it is on main tab else will fail…by that you can know the transition