Tkinter multi-frame resize

You have widgets nested inside widgets. Even if you have the notebook set to expand properly in it's container, you need to also make sure that every container upwards also expands properly. You haven't done that. For example, ask yourself whether the canvas has been set up to properly grow inside of lower.

Since you are starting out, here is what I recommend. Instead of trying to get everything right at once, choose a "divide and conquer" approach. First, create frames for the major areas of your GUI. Do nothing but those frames, and get their resize behavior to be exactly what you want. It helps at this stage to give each its own color so you can clearly see where the widgets are. You can always change the color later. Also, if you only have a couple widgets, or all your widgets are oriented horizontally or vertically, pack is often easier to use than grid.

For example:

upper.pack(side="top", fill="x", expand=False)lower.pack(side="bottom", fill="both", expand=True)

Once you have these major pieces resizing appropriately it's time to solve the problem for just one of those areas. Pick an area, and do the same: add in its children widgets, or subdivide into frames if you have areas within an area. Once you have this working, lather, rinse, repeat.