copy and paste
copy - select by the dragging mouse with left mouse button pressed, double click to select a word, triple click to select the whole line.
paste - middle click
To copy with mouse and paste with shift insert
konsole -> Settings -> Configure Shortcuts -> Search for "paste" -> click at the empty space corresponding to "Paste Selection" and "Alternate" -> Custom -> Shift + Ins -> Reassign -> OK
This also helps if you double click to copy and paste with <Shift> + <Insert>.