Feel free to fill in anything you like into the field "source", e.g. "Me", "Prayer", "Stormie Omartian" (the field is a bit short for this, though).
Same with the field "reference". The only caveat: the reference has to be unique in the current Remember Me version - e.g. "Pray for kids' protection 1". The cloud won't replace anything unless you intentionally press on the "Scripture" button to retrieve a passage from an online bible and press "Paste".
It might make sense to create a dedicated account for your prayers. Remember Me 6 will make managing multiple accounts easier. You can have a first glimpse on
https://doc.remem.me