+1
Squash is an amazing sport so it would be really nice to have it in the list.
On most Garmin watches, you can add whatever sport you wish. Check out your user manual - an example for the Forerunner 735XT is here: https://www8.garmin.com/manuals/webhelp/forerunner735/EN-US/GUID-6D055816-2C05-49F5-8BE7-B4E0A7C09570.html
On watches supporting the ConnectIQ technology you can find a plugin in the ConnectIQ store for almost any sport you can imagine. And if you can't, you can write one yourself, or hire someone to do it.
Also have a look at this similar thread about badminton: https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-mobile-andriod/204741/badminton