If starting from scratch, you can change the subdivision by increasing the steps.
But this will not work for existing patterns. (Make a copy of the pattern first) You need to bounce the pattern to clip, and then re-convert it back to Step Sequencer by selecting a different resolution (32nd notes). But by doing so, you lose the column names and empty rows will be deleted.
Another option you can try (especially if the pattern you want to convert is very complex) is to insert another midi track and route the midi out similar to the existing track and have 2 parallel tracks to do the job. Then you can have a new track/step sequencer to handle the higher subdivision notes.