Final answer:
To activate the default reviewing pane vertically in Microsoft Word, navigate to the Review tab, find the Tracking section, and select Reviewing Pane Vertical from the Reviewing Pane dropdown list.
Step-by-step explanation:
To activate the default reviewing pane vertically in Microsoft Word without changing the current view, you need to go to the Review tab on the ribbon. Once there, look for the Tracking section. In that section, you will find the option for the Reviewing Pane. Click on Reviewing Pane and then select Reviewing Pane Vertical from the dropdown list to activate it. This will open a pane on the left side of the document that displays the comments, revisions, and other tracked changes in the document, without altering the current view of the document itself.