In the Audio panel made for Baron 58 panel, all LEDs are connected with PCB by very thin short wires as I show in this picture:
Also, as I prefer to avoid using any PCBs when possible in simple projects, this can be done by way of buttons simply being attached to a piece of plastic (by thermo-glue) and thin wires laid to the connector or multiplexer board:
There are no problems with wires bending, because they barely move and never get broken, even single-core (if the wire used is thin enough).
The buttons are cut with a “paper knife” from a 5 mm thick PVC plate. It only takes a few minutes for one button. Then it is finished with sandpaper and glued to a piece of PVC with a thickness of 1-2 mm, the size of which is slightly bigger than the button.
Note: The LEDs used as an indicator with a typical 360 Ohm serial resistor seems to be too bright and unrealistic. Test your LEDs (preferably in the assembled device) with different resistors starting at 1 kΩ.