I see you have indent and un-indent buttons, but it seems it only affects the current line and dosn't care if the "indention" is correct or not.
i can confirm that Horus is ignoring the indention of pasted text. you´re right, this is annoying. i´ll fix this in the next version.
till then: the indention (by clicking the button or pressing tab) will affect on all selected lines (and not only the current). so select the copied parts and press tab to indent the whole selection
