you actually need to use tags:
for wgen - the wall generator:
- first select the entity
- use the command DT 5
- deselect it
- select the door it activates
- use the command T 5
DT in this case means Destination Tag
and T is for Tag (and you need to use a seperate tag for what your want to activate)
you can browse all tags set on a level in menu option 8 (tag info)
linking only works for switches (like the doors on E1M1)
but tagging them like this should work
the difference is switches don't destroy the energy door - only toggle it
( for the large generator (xgen) you don't have to it automatically destroys all energy doors)