Why is Shift+Insert no longer possible? You use FN+Insert for Scroll Lock
On the microsoft keyboard I tried, it became a 3rd function on the Printscreen/SysReq key. The keyboard did not contain an 'FN' key.
Shift + that key activated 'Print Screen', rather than paste text. Only inside MS Office did the button behave like the insert/overwrite toggle switch, but still couldn't get a 'paste' out of it.
Which is really unfortunate, since it's a feature I use all day, every day... Especially when you work in a mixed environment (Unix shells), it's the only universal shortcut to paste stuff.