John does not wish to write these other things but would like to come say the words to them. He is not saying that he would write them with something other than paper and ink.
Here John speaks of this other church as if it were a sister to the readers' church and the believers that are a part of that church as if they were that church's children. This emphasizes that all believers are a spiritual family. (See: [[rc://en/ta/man/translate/figs-metaphor]])