The answer to the first question would depend on how your data is formatted.
If you had a wide table, like this …
Then a Bars command can make this graph.
If you take the same data and Flatten it, so it looks like this:
Then you can use a Pivot command.
Either approach gets you the same graph with one command, no split canvas needed.
However, your second question indicates you want to have different legends for each bar.
The legend command has an option to only list items for the selected axis, when you have a split. Thus, if you use a split axis, you can have three Legend commands where each one is for a different axis.
This graph is made by splitting the x axis twice. Then the Pivot command is copied and pasted twice. One command is placed on each axis with a mask to limit the data to one of the categories. Then the three legend commands are added as shown.
Is this similar to what you want to do?