How to disable Office 365/PowerPoint's "Design Ideas"?

Choose File | Options

Click General

Look for PowerPoint Designer on the right

Remove the checkmark next to Automatically show me design ideas

Click OK

For Macs - On the PowerPoint menu, select Preferences.

Under Authoring and Proofing Tools, select General.

In the General dialog box, under PowerPoint Designer, clear the Automatically show me design ideas check box.