Ctrl+shift+Button1 click is not doing the same as Ctrl+shift+B

In the settings>keymap I can see that to go to a "type declaration" there are two default shortcuts. Ctrl+Shift+B and Ctrl+Shift+Button1_Click so I would expect both of them to have the same behaviour: when in  a symbol, go to the type declaration of the symbol. However using the shortcut with the click opens the type declaration in a new intellij window, whereas Ctrl+Shift+B opens it in the same one. This is confusing, why do they have different behaviour?. Ultimately what I want is to make Ctrl+Shift+BUtton1_Click open declarations as another tab in the same window, just like Ctrl+Shift+B does. How can I change this behaviour??