Set repeat notification for messaging on 7 Nougat?

Hey all;
I've got an LG Fiesta (2) on TracFone with Android 7 Nougat.
I am using the stock messaging app, and want to set notifications to repeat. Currently, I get the notification only once.
I have Googled several times and found that there should be a setting in Notifications, but I cannot find any option to repeat.

Do I need to install a different (SMS) message app, or is there a (very) hidden setting.

Thanks for your help
ET

 

Thanks. I used and liked Textra several years ago on another phone running KitKat, but had forgotten about it.