Manjaro Linux is based on Arch Linux, and Arch includes a package "util-linux" which provides two services for TRIM, "fstrim.service" and "fstrim.timer".
From my brief research I found that it is reccomended by the Linux community to run "fstrim" no more than once per week. This is to prevent excessive wear and tear on the SSD.
To enable automatic Trimming, run the following commands in a terminal.
systemctl enable fstrim.timer systemctl start fstrim.timer
To check the status of "fstrim.timer", run the following command.
systemctl status fstrim.timer
The status output should show:
Active: active (waiting)
That's it! TRIM is now enabled and will run once per week with the fstrim.timer service.
Source: Arch Wiki - Solid state drive