the "conner" shape of outline,

while drawing a shape by Rectangle tool with “Create Outline Bline” option enabled, I faced a problem to get a smooth rounded (or sharp) conner,

Can anybody give me a hand?

Thanks in advanced

When both tangents of a corner are zero, the corner is flat. You should pull the tangents ducks to get a rounded or sharp corner, depeding on the rest of parameters (split tangents, sharp cups, etc.)
See the documentation page:

thanks, drawing with synfig studio is fun :slight_smile:

but before you can master it, you need to throw out some of knowledges you have learn from inkscape, illustrator, xara, etc…