What you asked for is a feature called indicator on indicator. Many brand name platforms have that.
Once the spread indicator is applied, you can add any indicators on top as if it is a data series.
There is also another way to track customized pairs. Its called user defined symbols, some platform call that customized symbol, etc.
What that does is that you can create a symbol of your own that track basically anything - spreads, weighted index, etc.
You can then quote and chart these symbols as if they are normal symbols.
NeoTicker can do both, but check your current platform first, it may already have what you want, just that you do not know how to look for it, and now you know