Apply current track's DSP does not resample

Apply current track’s DSP does not resample the sample before applying the effects, it plays it as-is at your current renoise sample rate. That doesn’t seem to be working as intended, or at least should be documented.

Would be nice to make it also take transposition into account, along with having apply FX available in scripting.

Unrelatedly, duplicating a sample in an instrument with a vst-instrument/fx-alias already there still makes you automatically change to the plugin tab btw.

This is indeed intended. If you want to resample and/or apply other sample properties you can always “render to sample” in the pattern editor.