How to add trendline over multiple series and a segment of x-value

[progprog]

How do I add a trendline that covers multiple series and over a partial
section of a series (for example, one for the first 5 x-values, and one for
the next 6 x-values for data from 4 series)?

 

[Bernard Liengme]

The first part is not possible (or I do not know how to do it!)
For the second part, rather than add trendline use TREND to fit each partial
dataset and add the results as new series in the chart.
best wishes