In Indicators this is a table, not a matrix pane: there is no renderer that ignores the time axis, so the kScript (legacy) month-by-year grid has no Indicator form today.
The nearest form is render.table over string slots: bucket bars into months from time.bar_open_sec, keep the last N monthly returns in module-level variables, write them into rows x cols string slots in finalize(), and the chart shows the newest complete row of the table (Plotting).
What stays on kScript (legacy): requestBars for daily history independent of the chart interval, plotMatrix with its summary rows and the highlighted forming month; run the original with Use kScript engine.