I am trying to understand the issue here. So, you created _vcd_orgId as an input and once you registered that WF, that input disappears from that WF input form yet it exists and even has a value which gets printed.
So, now there can be 2 scenarios
One, you want the value of _vcd_orgId accessible to you on the input form itself. For that you can use the Bind Field feature and bind _vcd_orgId to another variable, here orgId.

Second probability, if you want to change the value of _vcd_orgId whenever you run the WF on the input form, you can reverse bind _vcd_orgId to a custom input variable orgId and whatever goes into orgId will automatically be passed to _vdc_orgId.

Bottom line, _vcd_orgId can't be seen on the input form during WF run. However, it is there and we can use it anyway we want.
Mark it as accepted if it helps. Thanks.