I’m attempting something similar.
My bokeh serve application’s look in 3.0 is quite different from 2.4.0.
The page has Div, Button, RadioButtonGroup, MultiChoice, and
DataTable elements.
The Button elements seem the most different. They occupy about 50% of the previous screen area and have changed the flow and layout of the other elements. Buttons seem to be less tall and less wide by default now.
I’m watching this thread to see how to get back to 2.4 sizing and placement.
Apparently CSS changed to per-object specification, which is fine, but it’s not clear how to migrate back to the previous look and feel.
This tip and bug report seems to help but again, it’s not obvious.