How to connect a second estop

Hello everyone,
I currently have one emergency button connected to the EStop pin of my MK3/9 Board. This button is working as I'm expecting it to do.
As I got a new vfd that can switch a relay in case it goes into a fault state I would like to incorporate this into the estop routine. It should cause the software to go into estop if the vfd reports a error on this relay.
My first impulse was to just connect the relay to one free input on the input board an configure it as a estop pin, however I quickly noticed that there is no way to configure a normal input as a estop.
Next I tried using one of the limit inputs where I set the estop flag, for whatever reason this does not work either for me. Somehow the estop flag for the limit inputs does not work on my configuration (hard and softlimits are enabled).

I finally settled on connecting it to a input and configured this input as a shortcut for estop. This works ok most of the time, but it does not work while jogging the machine manually (However its unlikely that the vfd will report an error during manuall jogging).

Of course i could wire it up in series with the emergency button, but I would like to have it separately.

How are you handling this?

Best Regards,
Klaus

Why separately? Is the best way!

My personal preference will be in series.
Because I think that one machine it must have a single E-Stop, no matter if it will be triggered manual or bay any fault from spindle, motors or every other fault connected to emergency stop.
Just my personal thought, maybe I'm wrong.

I'm also wondering, why do you want second pin?
Have you considered Error pin? It will trigger e-stop. And it is designed specially for this.
EStop pin implementation is different that other pins. That is why input pin can not be used as stop pin.
Limit pins will trigger e-stop only if machine is moving in their direction.

combining the two on one pin is mainly main due to my laziness in adapting the cabeling for the current emergency button. It currently connected directly to the board without any opto isolation and I don't want to connect anything from the vfd directly to the board. But you are right it might be a good time to fix this.
The Error pin sounds like a good Idea as well.

Is there any functional difference between the Error pin and the E-Stop pin?

An E-stop circuit/relay should normally consist of ONE series circuit with all sensing or stop indicators NAND'ed together in one string.
This disconnects all motive power on the machine, I have shown elsewhere where a VFD can incorporate a power input contactor safely.

Estops and Error pin behave same way.