Hi Alex,
Sure:
create a new project
create an audio track and put some audio on it
create a bus and route your audio track to it
insert an External Insert on that bus and set it up to use an external effect (ins and outs, latency)
solo that bus
Dean
EDIT: that was for 18719.
One more Edit (that'll teach me to post before having coffee),
For the other problem - CWBRN-24189:
create a new project
create an audio track and put some audio on it
put an external insert on that track that uses one mono output (eg, output 3)
Try and use the other output in that stereo pair (in my example that would be output 4) for something else in the project
Since one of the outputs in the stereo pair is used it causes the other output to be unavailable, just as if you had used a stereo pair instead of a mono.