Hi, I did not try, but maybe there is a Kind of work around for what you want to do:
If the Plugins/Synths to be controlled react to midi you could set up a midi channel and use a Controller and the midi sends of the midi track to let the same Controller follow multiple instruments.
PS.: My post Counter does not reflect the truth… I am in the Forum since Ages and I used to post a lot. One of my ideas was to make Automation tracks INDEPENDENT from other tracks, i.e. allow to route them to various other tracks/Instruments. A Signal is just a Signal and it should be possible to route it to wherever we want to.