You can use CSS display & visibility options.
- visibility:hidden; will make the objects invisible but they will remain there. Useful if the element has a child you want to see (like the search bar)
- display: none; the object won't be rendered, and you won't be able to render children elements either.
Create a tiddler, tag it with $:/tags/Stylesheet
Use developer tools (F12 on chrome) to find which classes you need to hide
Add the classes with the appropriate properties
.something {display:none;}
.something-else {visibility:hidden;}