When pasting merging should not be done automatically

Using Pinta 0.5 on Windows XP sp3 / Ubuntu 10.10.

Most of the time I use image editor to merge two or more print-screens. So I do the following:
1. new image 1
2. print-screen of desired window and paste into image 1
3. new image 2
4. print-screen of desired window and paste into image 2
5. new image 3
6. go to image 1 window and use Rectangle Select object and select desired picture and copy it
7. paste the image into image 3
8. go to image 2 window and use Rectangle Select object and select desired picture and copy it
9. paste the image

In Pinta pasted image is merged into existing image and so made merged image useless.

In Microsoft Paint (Windows app) and Paint.net (Windows app) applications: image is pasted and automatically "Move Selected Pixels" is selected. The most important: pasted image is not automatically merged into existing image. It makes user possibility to move pasted object to new desired position. When object is moved underlining image is not damaged - it just behaves like two layers.

In Microsoft Paint when you click outside of "selected object" then pasted image is merged into existing image. In Paint.net when you select some other image from Tools toolbar like Ellipse Select object then pasted image is merged into existing image.

When Undo is made in Microsoft Paint you undo pasted image completely, so it disappears. In Paint.net you just undo previous action like selecting Ellipse Select object and you are returned into "Move Selected Pixels" state and you can still move the object.

It would be nice if Pinta would behave like Paint.net in this case or at least like Microsoft Paint. So do not automatically merge pasted image into existing image.