There are some difficulties to creat the system from those two indicators. RSTL (Reference Slow Trend Line) is more static indicator which is having big delay. It is 'Support Slow Trend Line'. Just for orientation only. It's like a zigzag indicator.

RSTL is moving with big delay.
And supertrend is producing false signal and having delay as well.
It is good system to filter the signals but not to create or to produce the signals.
To create the signals we need to select some more dynamic indicators.