I have a bitmap which I want to crop (using a vector) with rounded corners I can't because I need 2 or more paths? How can I do this?
There are two ways, one with selections and another one with masks.
For selections, you can check this tutorial. It basically creates a shape to use as the extraction. You have to select the Rounded Rectangle tool and in the Property inspector set the roundness to the value you want. Then draw a rectangle without fill over your image, paste image inside it and delete the stroke.
If you prefer masks (way better, because it can be easy to adapt), check this one. In this case, you draw a shape with round corners and paste it as a mask (Edit > Paste as Mask) on top of the photo. The advantage is nor only the editing possibilities, but the re-using of this mask in other photos.