List of Features Not Supported in External Axes Mode

Listing them here for now. Hopefully eventually all will include warnings in the code:

Feature	Why not supported
panel	fundamentally different approach
y_on_right	because the information is stored within the panel object; in theory, maybe this could be supported.
figscale	mplfinance has no access to the Figure (when in external axes mode)
figratio	mplfinance has no access to the Figure (when in external axes mode)
figsize	mplfinance has no access to the Figure (when in external axes mode)
title	mplfinance has no access to the Figure (when in external axes mode). Use axtitle instead (or don't use external Axes mode).
volume=True	user must specify volume=<AxesObject> (since all Axes are external, mplfinance otherwise doesn't know which Axes to use for volume).
x-axis ticks only on the bottom plot	since Axes are external, mplfinance has no idea which one is on the bottom.
secondary_y	a secondary y is actually another Axes; so user must provide the secondary_y Axes object via ax=<AxesObject>
fill_between	this will take some restructuring of the code but can, in theory, be supported in External Axes Mode
savefig	mplfinance has no access to the Figure (when in external axes mode)
axisoff	user has the full list of Axes objects; let the user call ax.set_axis_off() for all of them.
tight_layout	mplfinance has no access to the Figure (when in external axes mode)
...	...