In Samplitude Producer 11 (hereafter abbreviated S11P), the Insert slots in the Track Editor or Mixer are where you would typically any VST or Direct X plugin effects to an individual track or to an Aux channel. You can add plugins to the Insert slots by simply clicking the down arrow for each one, and then choosing the effect that you want. You can change the order of your plugins by simply clicking and dragging one from one slot to another (a nice "undocumented feature"). You can also right-click on the Inserts section to open up the Inserts dialog.
Just like the Aux Sends in S11P, the Inserts are Post-Fader. I repeat--the Inserts are Post-Fader. This is probably my only complaint about S11P. In my experience, for an Insert to be an Insert, it is inherently pre-fader. I've never in my life seen a hardware mixer with Insert jacks that were post-fader. That being said, it seems that if the Inserts were going to be one or the other (pre or post-fader), they should most definitely be pre-fader. With the way that the Inserts function now (post-fader) they operate more like a "Direct Out with Loopback" (if such a thing existed) than an Insert. I'll also mention that in S11P's "big brothers", Samplitude 11 and Samplitude 11 Pro, the Inserts are pre-fader by default (as they should be), and you can change them to post-fader if you like in the Routing Manager.
The Inserts being post-fader has caused a few problems for me when using various plugins. The plugin that I have the most trouble with is Aptrigga. Aptrigga is a drum replacement plugin that can be used to trigger a sample (in my case, typically Kick or Snare Drum) from a recorded track. Because the trigger reacts differently based on the input signal that it's receiving, it messes things up when you try to adjust the Track Volume via the fader. It may cause the plugin to trigger when it should not (if you raise the fader too high), or it may keep it from triggering when it should (if you lower the fader too much). If you make any adjustments to the Track's volume Fader, you then have to re-adjust the threshold in Aptrigga to ensure that the sensitivity is set properly (which is a real pain).
Another example of a plugin that this causes problems with is a Compressor. A Compressor responds differently based on the strength of its input signal, so that when you adjust the fader, it doesn't just change the track volume as it should--instead it drives the compressor more or less, which affects the resulting sound (sometimes in a not-so-pleasant way). The same sort of problem occurs with a Noise Gate plugin. You can set the Gate so that it opens and closes correctly, but as soon as you adjust the fader, you have to re-adjust the Noise Gate settings, because it's now receiving a different-strength signal than before. I did contact Magix Support about this problem, and was told that "it is in the developers suggestion box." So I'm hopeful that this will be addressed in a future patch or update.
In the meantime, fortunately there are a couple of workarounds. The first is to use a volume fader/gain plugin as the last plugin in your insert slots. This way, you can keep the Samplitude Volume fader at a constant setting, which won't throw off your plugins. The downside to this is that you have to make your volume adjustments using the plugin, which would be a pain in the butt while mixing your tracks.
The other workaround, which is my preferred method when working in S11P, is to add any of your input-dependent plugins in the Insert slots of the Object Editor (by double-clicking the waveform object in the Arrange window) instead of the Insert slots in the Track Editor/Mixer. The Object Editor is inherently pre-fader, so you can add your drum-replacement, compressor, or noise gate plugins there, get the settings dialed in, and then any fader adjustments that you make will not affect the plugins.
The only downside to this approach is that you'll need to glue any separate objects in a track together to make a single object, or select all of the objects in the track and apply to all, but that's not too terribly difficult. I hope this tip will help someone else who may have encountered similar problems using these types of plugins in S11P.