Get text labels from column for line series in combination graph

I have several combination stacked column and line graphs. The X axis is a date, and I do not want this to change since this is a time series. I have 8 columns of data for the stacked column part of the graph and 5 columns of data for line series. The last line series data column is named Event and the Event cell for any specific date either has no value or a value of 1. The line series for Event is formatted with no line and with a symbol, to indicate the event on the graph. This results in a symbol appearing adjacent to the X axis for any date with an event.

I would like to display text from a column for this event series instead of the (meaningless) numerical value of the cells, or the category (which is the date). e.g. “Released v2” or “Thanksgiving”. I have seen examples (from this forum) of how to do this with x/y scatter plots, but those solutions do not apply to the combination graph.

Depending on the graph, a graph represents multiple years or months. The X axis has the major/minor grid turned on, with major interval = 28 days and minor interval = 7 days.

Is it even possible to have column-sourced textual data labels in a combination graph? I have been using OO/LO for 10+ years and do not want to go back to Excel (I am informed that this is possible with Excel).