I am using painting programs to cut, copy, paste and crop files.

In Pinta:
1. Click on "Rectangle Select" button in Tools section.
2. Click on Cut, Copy or Crop Selection from toolbar or menu Edit / Image menu.

In KolourPaint for KDE:
1. the same as in Pinta.
2. Right click on selection and select Copy / Cut / Crop.

Using right mouse click I am also very used from Microsoft Paint on Windows.

It would be nice if right mouse click would be added.