Allow the users to customize the sidebar (or the default theme) as follow:

• fixed size instead of resizable (with indication of desired size in px or %)
• word-wrapping instead of scrolling (for the latter it is enough to change the CSS as indicated in https://answers.atlassian.com/questions/35770140/customize-sidebar-of-default-theme according to the user selection)
• Allow users to customize the font type, color size, and other properties of the sidebar text.