Persistent chart node

I am using the chart node to plot a live timeseries (humidity). When I restart NR the graph is reset. Which is the best practice to keep it persistent?

Best practice is to not use any live chart or if, then those should have short periods and/or not much data-points.
Charts are tools for analyse. But to do analyse it does not involve sitting and watching chart with 24h full of data and react on next data income. It really is to have the data and ask visual representation of it as needed.
Of course - for long running process, having periodically updated chart to see the things going in wrong way would help, but even then, the chart is not best tool cos it does not alert but just shows the conditions.

So if concept of analytics is treated as it should, the charts should be created on demand and filled with just right amount of data to do the analyse you need. For that purpose I think the easiest way is to store data to influxdb and use it with grafana. And yes, the grafana elements can be included into node-red dashboard but is it really needed - up to you.

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+1 for InfluxDB + Grafana.

...but if you must...

Add a change node to the output of the chart node formatted to save the chart output to file context.
Then add an inject node to the input of the chart node, to inject the file context (that you saved above).
Set the inject node to inject once.

context

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