Your RingCentral for Windows desktop app actually allows you to add favorites and you can do a one button click to start a fax to the desired number.
1) When you open your RingCentral for Windows click on the contacts icon in the top center of the screen.
2) From the contacts screen click the + button on the top right of the screen to add a new contact.
3)Enter a name and the fax number you want to have set as a favorite.
4) Then click save.
5) Once the contact has been saved click the star icon to the right of the contact to make it as a favorite.
6) Once the star has been selected click the Star Icon at the top of your RingCentral for Windows screen.
7) Once in the favorites screen you will see the fax icon next to the contact you just created. If you click here you will start a fax with the fax number automatically entered. Simply attache your document, type of note if needed, select your cover page and press send and your fax will be on its way.