GTR1 does have an EMA capability: sgema(...)

Interesting. It does not show up in any of the GTR1 documents I have.

But it doesn't do what I need. It does EMA of a predefined stock field. I want the EMA of a computed field. Ditto for SMA.

Fields:
tr1: max(minus(hgprc(1,1),gprc(2)),abs(minus(hgprc(1,1),gprc(2))),abs(minus(lgprc(1,1),gprc(2))))
myema: sgema(tr1,1,14)

Steps:
nas100.a != null
myema top 10

Error message:
"field8 is not a signal field: field9=sgema:field8,1,14"
gtr1.net: GTR1 Backtester - NAS-ATR14

To compute ATR(14), you need to do this for each stock:
tr1: max(minus(hgprc(1,1),gprc(2)),abs(minus(hgprc(1,1),gprc(2))),abs(minus(lgprc(1,1),gprc(2))))
and then take the EMA of the last 14 days of them.

But, who knows? Maybe GTR1 has the capability to add your own computed field(s) to stocks and I just don't know to do it.