I know it can be frustrating for organists to play the hymns and at the same time to read the words. While doing this, sometimes your tempo might become unstable and sometimes you can forget which verse the congregation is singing.
However, when you play hymns, I don't recommend reading the words too much because you have to focus on music (studying the text beforehand is a must, though).
One way to know which verse you are playing is to prepare the different registration in advance for each verse. If you remember the order of stop combinations for different verses, you will know which verse you are on.
Here's a video I made with demonstration of how not to get lost between the hymn verses.