RUPEE SYMBOL KEY

You could create a shortcut in system preferences > keyboard > text > replace with.

But also use Keyboard Viewer to check whether you already have it on the shift, option, and option-shift levels of your current layout:

https://support.apple.com/guide/mac-help/use-the-keyboard-viewer-on-mac-mchlp1015/10.14/mac/10.14

To make a text replacement for the ₹ in Word, go to Word > Preferences > Autocorrect

In general, for any problems with Office, use another forum

https://answers.microsoft.com/en-us/msoffice/forum/msoffice_word-mso_mac