I was struggling with this same situation. Here's what I did:

• Right click table select properties
• Select Columns from the top banner
• Select the pencil icon (edit) of the column you're working on.
• Select definition from the top banner of the popup window
• In this Datatype dropdown you can select the character varying datatype.

For whatever reason it's only available in this edit menu, not when you're setting up the table.