FN per Layer Toggle/Lock(?)

[drifting forum]

Option to Enable a layer with 1 key (not swap with main)

ie:

1. Main Layer
2. FN 2 Layer with Only arrow keys
3. FN 2 Toggle. Enables FN 2
4. Main layer + FN 2 on top

Currently the FN Lock swaps the selected layer with the main layer (ie, would have to re add every key)
Also, current FN lock requires binding the FN Lock button to the FN layer we are trying to swap. This means I also have 1 less button on the layer.