support markup language method of editing math objects.

[reos-rcrozier]

Is your feature request related to a problem? Please describe.
Math (formula objects) has been implemented in writer which is excellent (and means #4049 could soon be closed). However, only the gui method of entering equations is possible (the equivalent of the 'Elements Dock in LibreOffice). This feature request is to implement the markup language method available in LibreOffice. This would also expose the full range of meth formulas available.

Describe the solution you'd like
Provide a method of editing formulas using markup language, perhaps in a box under the elements editor in the sidebar.

[rpear]

The option to Insert > Formula object In Compact View is not present, it only appears in the Tabbed View.