I have a V-rotary panel. I want to assign using one key to listen to the IFB source and talk to the Global IFB destination. Note The IFB source and the Global IFB destination are wired to the same 4wire MVX port
Yes this is possible. The listen andtalk keys on the Rotary panel can be programmed independently so he can have alisten to 4wire and talk to the IFB 
Step one go to cards and ports > select the 4wire port(port 16) and set Split mode enabled Also set the port to be a Global IFB 

Step two route the IFB source port (AuX-1)  to the 4wire Global IFB destination port (PTB) Go to Configuration > localadvance > forced listen screenMake xpt between AUX-1 and PTB 


Step three program the relevant talk and listen keys on the V-rotary panel AUX-1 = the 4wire input label to thematrix PTB = output label of the same 4wireport (Global IFB destination port)When a user presses their "PTB" talk key it will dim the AUX-1 input