AddtoComposite or staticvar to build a indicator

I would like to sum up all rsi values from all my stocks in my watchlist and create one rsi_total_indicator. If this is possible and can I backtest this indicator for certain rules.
For example buy totalrsi < 30 then … and see this additonal in the explorer
How can I program this indicator for AddtoCompite I see example but not testing and for staticvar I don´t see examples for this to learn or can someone help me for this indicator.
Thanks for any help.

Everything is possible, but it requires some effort. If you had used the forum’s search option, you would have easily found this thread from a couple days ago: