Open an impress document, select slide layout chart+title, double-click to enter
your data. You get a column chart with dummy data.
Now try to make a stock chart. You get a lot of problems.

A
Goal: stock chart type 1 (low-high-close)
Click on “Data Type†and select “Stock†variant 1, Finish.
View chart data table and enter your values. Finish.
Problem: You get a secondary axis.

B
Goal: stock chart type 3 (volume-low-high-close)
Click on “Data Type†and select “Stock†variant 3, Finish.
Problem: All data columns are gone.
Workaround: First add a column and enter the data, then change chart type from
column to stock variant 3.

C
Goal: Change stock type 1 to 3 or stock type 2 to 4
First try: first change chart type, then add column.
Same problem as in “Bâ€, the data columns are gone.

D
Goal: Change stock type 1 to 3 or stock type 2 to 4
Second try: first add column, then change chart type.
View chart data table and click on “insert columnâ€.
Problem: You don't get a single column, but a new data series, with messed up
roles or you get a new volume column.
Workaround: Change chart to column chart, add the open-column, change chart type
back to stock variant.

Suggestion: If user changes chart type and there are not enough data columns,
add a data column with dummy values. If it is a change within stock variants,
then keep the already given roles.