It seems that SAP 9.2 PL06 have changed some logic that prevent us from controlling the Left-position on added tabs. In the past you could set a left-value and control the left-most position but is seems that is ignored in SAP 9.2 PL06 and new tabs are always created as the last (right-most) tab.
Also it seems that on some windows adding new tab also change the order of the existing SAP Tabs in random order.
An interesting note is that this also happen with SAP's own UI Edit mode so 99% sure it is a bug from SAP side.
We will investigate this together with SAP Support and update this article as more information become available.
Update (2017.02.22): Now logged to SAP Support as Ticket 92100/2017
Update (2017.02.23): The issue is now under investigation by the SAP developers
Update (2017.02.27): SAP Support have confirmed this as a bug the they will fix in SAP 9.2 PL08. They have created SAP Note 2433070 on the matter (at the time of this writing the SAP Note is not released though)
Update (2017.03.03): We asked SAP, if there are any workarounds we could apply and unfortunately the answer is that there are no workarounds available and people need to wait for PL08 :-(