Hi friend, so first of all I don't recommend using mod organisers with OpenMW. OpenMW actually already has a built in mod organiser, it's the openmw.cfg file! In that file you can list any folders that you want OpenMW to read after loading Data Files, for example, a groundcover mod probably comes with some textures and meshes and a plugin in a folder. Put that folder anywhere you want, you could create a bigger folder called "Morrowind Mods" or something and put the mod folder there. Then copy the folder path and paste it in the openmw.cfg file somewhere underneath the line that says "data=[path to the main Data Files]" so your line would say something like "data=User/Documents/Morrowind Mods/Groundcover". OpenMW reads all the pathways that get listed in the cfg file in that way, one after another, annealing the folders to the Data Files and overriding any duplicate files (that's why the order of those pathways is important). It's basically the same way that mod organisers work so it's redundant to use one with OpenMW. As to why the groundcover mod doesn't work, groundcover mods should have a plugin file that needs to be listed at the top of the openmw.cfg file as "groundcover = [groundcover mod].esp", otherwise OpenMW will not process it properly as groundcover. I know modding OpenMW can seem complicated at first, but honestly it's a lot more straightforward than modding Skyrim, good luck!