I was looking for a Wappler visual solution, not a code solution in case i had missed something in the Database Manager
Knex supports medium text. easy enough to edit knex files. I dont see the solution as having to mess about with migration files as that, in my mind, defeats the whole concept of a Visual App Builder.
Unless anyone else knows an answer i guess it's a FR to add it to the interface.
For the meantime it's an easy change with an external editor as a one off.