When patches are added or changed, the UI is no longer accessible by double-clicking the instrument name or clicking the “ext.editor” button in the inst. settings. This doesn’t seem to be a bug with hexter, since this behaves correctly in rosegarden, and in the “ghostess” DSSI host. Curious thing is, this bug also doesn’t occur in renoise with other DSSI plugins like whysynth.
Even saving, restarting renoise, and reloading the module doesn’t solve it. Anyway, here’s a test file with two Hexter instruments. The second one has patches added, and so there’s no way to get the interface.