Logic 10.5 sees the plugin as "Midi-controlled effect"

With the introduction of Logic 10.5 some things have been changed in the workflow and in the way the effect plugins are listed. If an effect plugin has Midi functionalities (for controlling parameters via Midi), it is listed as a "Midi-controlled effect" and can only be inserted in channels with Midi support, for example in Instrument tracks and Aux tracks, but not in plain Audio tracks.

The AudioUnit protocol requires to specify a category for a plugin, and for effects there are two categories:
- "Effect" is just an effect with audio inputs and audio outputs
- "MusicEffect" also adds Midi ports

All GSi AU effects are categorized as "MusicEffect".

In order to insert an effect in an audio track, follow these steps:

1. create an AUX track and insert the effect; in the input section of this track select a bus of your choice, for example "BUS 1"
2. in the output section of your audio track, replace Stereo Out with "BUS 1 -> AUX #"

Now your audio track is routed directly to your AUX track, gets processed by the AU effect, and goes straight to the stereo output.

With amvbience effects such as delays and reverbs, you might want to have more than one track to be processed by the same effect.
This is a way to create an effect bus:

1. create an AUX track and insert the effect; in the input section of this track select a bus of your choice, for example "BUS 1"
2. in the SEND section of your audio tracks select "BUS 1 -> AUX #" and adjust the amount of signal to be sent to the AUX track

Now, since the dry audio signal would take two parallel routes, one through the track's output, and another through the aux track(s), you'd have to defeat the dry signal passing through the effect(s). The effect plugin should have its own "DRY Level" knob, make sure this is set to zero.