Newbie Question: Where is Timewise?

I'm new to scoring with musescore and I've already run into a bit of difficulty. I've inputted a few measures of 3/4 time with 3/4 notes and now I want to go back and insert some additional notes in these measures, but within the same staff. I went to the online Help Handbook to see if I could find out how to do this, and apparently this is accomplished by using the Timewise command, which is accessed from the N dropdown. But when I click on the N, where Timewise is shown in the Handbook, my dropdown shows Insert instead. Fine, sez I, so I try insert. Well, it allows me to insert notes into a measure, but the note is inserted at the beginning of the measure only and it moves the existing note over. I don't want this. I want the existing note to stay put and be able to add notes around it as I see fit, in this case I want to add trailing quarter and eighth notes. So, what do I do to get Timewise to appear in this dropdown?

I've had a look at Edit/Preferences, but that doesn't seem to be able to do what I need.