[BUG] Overflow in Sidebar with Centreralized Theme

[kookma]

Describe the bug Referring to https://github.com/Jermolene/TiddlyWiki5/discussions/6167#discussioncomment-1769002, when centralized theme is in use there is overflow from sidebar! For example in More > Pulgin tab!

To Reproduce Steps to reproduce the behavior:

1. Go to https://tiddlywiki.com
2. Change theme to Centralized
3. Change the sidebar layout to Fluid Story
4. Open the sidebar > More > Plugins
5. See the overflow from right with no scrollbar to reveal the part of content overflowed.

Expected behavior I may recommend no overflow by using proper CSS with simple flat style in sidebar!

Screenshots

TiddlyWiki Configuration (please complete the following information):

• Version 5.2.1

Desktop (please complete the following information):

• OS: Wi10
• Browser Chrome 96

IMPORTANT Centralized surfers for correct laying out the sidebar! I may recommend to have a look Notebook from @NicolasPetton By default in centralized the sidebar shall be closed When sidebar is open the story river shall be placed in the center of remaining space NOT in center of viewport

[Jermolene]

Thanks @kookma