Cant reassign controls for a Core Remap in RetroArch -help a NOOB

New to this Forum and glad I joined! Setup - WIN10 PC, latest vs of RetroArch, five USB joysticks with 10 buttons (IPAC for arcade cabinet)

I am setting up controls in RetroArch. with NO cores loaded I go to Setting and then input and set my input user binds. I have device type set to RetroPad w/ Analog and use the Right Analog. the joystick and buttons are recognized and I assign the controls with ease, save configuration, and when I go out of retroarch and back in I still see the updated users controls. Great!
But now lets say I want to change some control assignments and create a Core Remap. I load in the core that I want to assign custom controls, see attached pic for (stella). go to the quick menu and then controls. I see my assigned controller setting but I cannot change them. when I hit ‘enter’ nothing happen. I can save/load the Core Remap but unable to change those three little dashes to a new assign control action for that specific Core.

I have scrubbed the forums and have watched many vids on YouTube and it seems easy. you just click on the controller for the action and it re-assigns it.

What am I doing wrong?

Matt

In the controls menu, you press left/right to cycle through the core functions.