I create a wx.TextEntryDialog as follows:
import wx
dlg = wx.TextEntryDialog(self, 'Rules:', 'Edit rules',
style=wx.TE_MULTILINE|wx.OK|wx.CANCEL)
dlg.SetValue(self.rules_text.Value)
if dlg.ShowModal() == wx.ID_OK:
…
This results in a dialog box that is too small for my needs, and that is not resizable:

My question is: How can I make the dialog box larger and resizable? I tried adding the flags wx.DEFAULT_DIALOG_STYLE and wx.RESIZE_BORDER, but that had no effect except to replace the text with dots:
dlg = wx.TextEntryDialog(self, 'Rules:', 'Edit rules',
style=wx.TE_MULTILINE|wx.OK|wx.CANCEL|wx.DEFAULT_DIALOG_STYLE|wx.RESIZE_BORDER)

Time to learn how to write your own dialogs! 😉
The built-in dialogs such as
TextEntryDialogare only for the most basic programs. If you need much customization, you need to write your own dialogs.Here’s an example, this should work for you.