Hi GoldWeed,
Do you mean the "X" shown as the following screen when Reading Pane is turned on?

Does this look same as your Outlook Client? I've checked on both Outlook 2016 and Outlook 2013 and the location of "X" hasn't changed. My Outlook 2016 version is 1803 Build(9126.2152).
Please post back with the detailed version information of Outlook for further assistance.
Besides, if it is convenient for you, you could also share a screenshot here. If you cannot put the screenshot here, you can upload it to OneDrive (https://onedrive.live.com/) and then share the link here.
If I have misunderstood anything, please feel free to post back.
Regards,
Perry
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