As bokeh.plotting is a slightly lower level interface, you will have to do the "stacking" by hand. Here is an example that stacks two bars horizontally:
It could probably be very useful to have a "stacked" util function that could automatically generate stacked coordinates suitable for use by hbar and vbar. A pull request to add something like that would be welcome, if you are interested in making an OSS contribution.
I haven't found any examples regarding the creation of stacked hbar plots (with bokeh.plotting.figure.hbar).
bokeh.chars.Bar has a "stack" argument, but there aren't any plots with horizontal bars to be found.
If possible, could you provide a small example?