environment variables, then other answers have already covered this.However, if you want to edit both system-wide and user-specific environment variables then most (if not all) of these answers are inapplicable in general case. On the left-hand side of that applet you will see a link that says Change my environment variables.You skipped "About → System Info" between these two. Who'd think changing environment variables could be anywhere else than under "About/System Info"... Then on the left side click About and select System info at the bottom.
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Going through "System" and then “Advanced system settings” - user account, then trying to access “Advanced system settings” will trigger an UAC prompt asking you for administrator password. in order to give regular users the opportunity to edit their own environment variables) Windows provides another way to access the “Environment Variables” dialog. Click that link, and it will take you to the same “Environment Variables” dialog for your user's environment variables.
If you enter the password, “Advanced system settings” will successfully open, but any user-specific changes you make there will apply to the corresponding administrator's account (! If your user has administrator rights, you will be able to edit both sections of that dialog: user-specific environment variables (upper section) and system-wide environment variables (lower section).
Now in the new window that comes up, select Environment Variables... There is a direct path in a more recent Windows 10: in the main Settings window, just type "Path" into the search box and options to jump straight to the variable editors will appear. Updated answer with a Power Shell method which should work when not an admin.
I'm not 100% sure on the admin part as I am on a company laptop, and I am usually prompted for admin actions and but I was not for Power Shell and this worked. From there, select “Advanced system settings” → “Environment Variables”.