If you want to clear the input edit or if you want to put something in and the focus is somewhere on the tabs just type ESC, the entire edit will be selected and have a focus.
If you want to insert a value with a base (radix) 2 or 16 use the unary operator & (for the base 2) or # (for the base 16). For example &10=2 (decimal), #10=16 (decimal). When you're using these operators then 'input' mode on the 'display' tab is ignored.
You can calculate more than one formula at the same time. To achive this use a semicolon in the global space, for example type '2+4 ; 5*10' and the result will be '6 50'.