How to change an eight rest to sixteenth rest?

How can I change an eight rest in the middle of an piece to an sixteenth?

There are several ways - here’s one.

Press Return to enable note entry, then I to enable insert mode. Press 5 to select eighth note, then Delete to delete the rest. Press 4 to select 16th note, then comma (,) to enter the rest.

…or don’t delete it at all. Just enable insert mode, select the rest, press 4 (or the 16th duration button).