"1" click the "Edit->Editing->Find" menu item, "Find" dialog pops up.
You can search from the topic's "Text","Hyperlink" description or Task resources information. You can choose whether match case when search.
"2" click on "Edit->Editing->Select" menu item, you can select all topics in a map or a topic and it's all subtopics.
"3" click on "Edit->Editing->Delete" menu item, by default it will delete current selected topic. and you can also delete other kind of mind map elements, such as note,symbol,hyperlink,relationship and so on.