So, is this a concern? Do I have to remove devices if I want to add another one? Or will Homey manage the memory use a swap file or something?
If you press on the rainbow graph, you’ll get an overview which apps the colors represent, which should provide a clue which app(s) are using up the memory. If it’s a concern or not depends on whether or not you’re noticing any performance issues.
I don’t think Homey uses a swapfile, not would it make a lot of difference because swapping still kills performance.