@martien - Apologies if this is somewhere up above and I am just missing it, but to your original question it also could just be that you are using the AU or VST version of the plugin. If you use the VST3 version of H-Reverb it DOES expose the reverb time to the host. I believe this issue is generally true of AU plugins and is one of the convenience/usability advantages of VST3. Here is a screenshot of a knob controlling the reverb time of the VST3 version of H-Reverb. No text label involved:
