This will open Word in Safe Mode. Now click on the File tab and select Options. In the Word Options, select Add-Ins. Browse the active Add-ins for ones you think may be causing Word to crash.

This only takes a second as you’ll find the AutoSave button displayed at the top of any window with an open Word document. It may default to the off position, so just click it to enable the ...

You may also open a new Blank document to check if the Design tab ... Once done, restart your PC for the changes to be applied. Word Online does not natively have a Design tab.