The Insert key without 3rd party apps on MacBook Air in VirtualBox running Linux Hardware setup

I use MacBook Air with what seems to be an English international keyboard layout. My Input Sources are set to Polish - Pro in the Keyboard settings.



Software setup

I run Debian 8.6.0 in a VirtualBox with a dwm window manager and xterm as the default terminal app there. The way copy and pasting works there is to select the text and press either Insert or the middle mouse bottom to paste the selection elsewhere.

My problem is that I cannot find a way to simulate pressing either of them. Is there a way to do it on MacBook Air with any 3rd party apps to remap my keyboard? I'm just looking for a way to copy and paste text in Debian Linux running inside the VirtualBox.

Here's what I've tried so far:

Insert key:


fnEnter
fnEnter, fnEnter
fnShiftEnter
Controlfnm
fnm (prints m obviously)
ControlfnShiftm
Controlfn&#x232B; (prints 5~)
ControlfnShift&#x232B; (prints 6~)
fni (prints i obviously)


Neither of which work.

Middle mouse button:


Press the touchpad with two fingers simultaneously.
Press the touchpad with two fingers simultaneously holding Shift.


Neither of which work.

References:


Where is the insert key on a MacBook Air?
How do I simulate the Insert key in Windows on a MacBook Pro?
Insert key on keyboard for Macbook Air Mountain Lion OS
It is not what I am looking for but it is a fine solution for the time being. If someone suggests a way to simulate the Insert key on MacBook Air I'll be happy to accept their answer.

A workaround in the Debian Linux itself

If you run xev to see what keycodes are actually being sent when you press keys you'll probably notice that fnEnter produces keycode 104 KP_Enter instead of keycode 36 Return. 

I decided to remap keycode 104 to Insert with xmodmap -e "keycode 104 = Insert".

As a result I am able to paste with fnShiftRight AltEnter.

References


Missing Apple MacBook Keys: How to map the INSERT key in Linux/VirtualBox
xmodmap on ArchWiki
Remap the insert key