Line Combo Chart that allows "Treat labels as text" to be disabled

[Sean Clark]

I have some data corresponding to specific dates throughout the year. I am trying to plot that data as a stacked column chart where the x-axis is uniformly distributed over time as opposed to one date's data per x-axis tick (which is not uniformly distributed over time).

This can be achieved by UN-checking the box at the bottom of the Chart Editor -> Setup tab that says "treat labels as text". By doing this, Google Sheets interprets my dates as continuous data, so I see a distribution of bars and gaps, where events occurred on specific dates but not others, just as I want.

In trying to add a line plot (e.g. mean) to the stacked column chart, I must select Line - Combo plot, which does not seem to have the check-box mentioned above, so all columns are adjacent one another and I lose visualisation of which dates had events on them.

Have I misunderstood something? 

https://developers.google.com/chart/interactive/docs/customizing_axes#discrete-vs-continuous suggests that combos of line and column charts allow the x-axis to be continuous, not discrete, but this is not what I'm finding.

TIA.

Sean.