This branch of research is in response the issue regarding scrollbars:

This seems to be one way to go to get the scroll bars all looking and acting the same way.

If you want to bring even more things into the same style, Have you considered using tk.ttk.Button() instead of tk.Button() for the toolbar?

tkintermd/frame.py

@@ -6,6 +6,7 @@
 from tkinter import messagebox as mbox
 from tkinter.constants import *
 from tkinterweb import HtmlFrame, Notebook
+from tkinterweb.utilities import ScrolledTextBox
 
 from markdown import Markdown
 from pygments import lex
@@ -141,17 +142,16 @@ def __init__(self, master, **kwargs):
 
         # Creating the widgets
         self.editor_pw = tk.PanedWindow(self.master, orient="horizontal")
-        self.editor_frame = tk.Frame(self.editor_pw)
-        self.text_area = tk.Text(self.editor_frame, state="normal", wrap="none", pady=2, padx=3, undo=True, width=100, height=25, yscrollcommand=self.on_mousewheel)
-        self.text_area.pack(side="left", fill="both", expand=1)
-        self.scrollbar = tk.Scrollbar(self.editor_frame, command=self.on_scrollbar)
-        self.scrollbar.pack(side="left", fill="y")
+        self.editor_frame = ScrolledTextBox(self.editor_pw)
+        self.text_area = self.editor_frame.tbox
         self.preview_tabs = Notebook(self.editor_pw)
         #make the previews
         self.preview_area = HtmlFrame(self.preview_tabs)
-        self.preview_html = tk.Text(self.preview_tabs)
+
+        self.preview_html_frame = ScrolledTextBox(self.preview_tabs)
+        self.preview_html = self.preview_html_frame.tbox
         self.preview_tabs.add(self.preview_area, text="Preview Format")
-        self.preview_tabs.add(self.preview_html, text="Preview HTML code")
+        self.preview_tabs.add(self.preview_html_frame, text="Preview HTML code")
         #add the areas to the paned window
         self.editor_pw.add(self.editor_frame)
         self.editor_pw.add(self.preview_tabs)