So there is one thing: Graswald only wipes unused loaded species on save, so if the slow-down is because your system ram is filling up, just save and revert the .blend.
I’ve tried having Graswald do a memory every species load, or system delete, but it can lead to instability when trying to undo—the kind that causes blender to crash and exit, not just stall, so I decided save and revert was the safest.
The easiest way to check if this was the issue would be to either reopen that blendfile, or to open the demo blend, which has a ton of systems, so if it runs quickly in viewport, you know that next time just save and revert. If this is not the issue, try—when it gets real slow—disabling graswald, and let me know if that speeds everything back up. If that fixes it, then there are some optimizations I’ll need to make (but they require removing a few features, so there is a tradeoff there).