the only creation argument of the object is the dll name of the plugin you want to use. the idea is that you can then open the abstraction, edit the parameters of the plugin, then click on save, which writes all the parameters to a array, so that when you click on load the values are read from the array and set in the plugin. when the object is created it automatically loads the current array (which will have been saved from last time the patch was open). this means you dont have to set all your plugin values every time you open a patch.
i had something like this set up using thomas grill's VST~ and Pool externals coupled with my GUi extensions, the patches are at http://whats-your.name/pd/. it was basically a 'rack' of vst's, with a tree to browse them, a patch to scan them on startup, X/Y param control etc.
its proably much easier to just install Plogue Bidule, which does the same thing. then you wont have to install toxy, tk extensions, mingw, add mingw paths to your system path, etc... although bidule seems to have gone commercial last i checked.. but it had better crash recovery (i implemented this by writing out the name of the most recently loaded plugin, and skipping it on next launch, but sometimes the corruption was caused by the plugin before that, and didnt appear till later, etc - luckily LADSPAs are much more well-behaved)
does anyone have a more elegant solution to this? it works fine excet for one problem: when i use the SIR convolution plugin, i think it remembers the filename of the impulse response that was previously selected but it doesnt seem to load it.
not sure what changed with VST2.4 which just came out, but in 2.3 and earlier, the only params accepted were floats normalized to 0.0 to 1.0, and MIDI. this means even if you implemented a state saving thing with Pool or PDContainer, you cant store stuff like the filenames. you have to tell the plugin to return a preset in its native (and nonstandard) binary-chunk format, which can then be saved to a .fxp (single preset) or .fxb (preset bank) file. im not sure VST~ does this.. once again, Bidule can..and porably AudioMulch..