how do i do categories in tasks without using the mouse?

I touch type, and I find the task set up window a bit annoying. I can select
the window on the task pane for the category; I can then type in my category;
but I cannot then, using the keys, close the category window. I have to
click on 'ok'.

I can then save the task and close the task without requiring the mouse.

How can I fix this?

Thank you.