I added the defaultText parameter to the Notifier.ShowTextDialog method but now when I go to use this method the defaultText already has a true block on it. This true block used to be on the cancelable parameter, but it changed when I added the defaultText parameter. Where is the file that deals with choosing blocks from this flyout menu so that I can change this default value?
See blocklyeditor/src/drawer.js line 592. My guess is that you'll also want to specify a default block for the defaultText and have it be the empty string.
You'll also want to add an upgrader in blocklyeditor/src/versioning.js to add an empty string for every existing occurrence of the block in projects.