Grafana graph for collated counter value from multiple series


I have a years worth of Graphite metrics data spanning over multiple series for two incremental counters ‘Started’ and ‘Completed’ for which I want to show a simple Grafana graph of how the value incremented over the year. All series does NOT have data at all times for the two counters.
My Grafana Series expression shall match multiple series as follows, e.g. n1.n2.n3.n4. *.n6. *.count.meter.count where node #5 in the expression will match the name of the instance which logged the metric (the name will vary with each deployment) and the wildcard in node #7 is either ‘started’ or ‘completed’.
I want to show the absolute counter value for the year so if it only incremented to e.g. 19 some 5 or 178 min ago I want the graph to show 19 for the whole time period since it was incremented to 19.
I started off with the groupByNodes(n1.n2.n3.n4. *.n6. *.count.meter.count, ‘sum’, 3, 6) which sums up and shows the two counter values for each time bucket but since each series does not have data for the two counters during the whole year it does not show the absolute counter value at all times.

Grateful for any help or suggestions,