I wrote an example action which rolls the excelling Table Magic web-based Markdown table editor into a Drafts HTML Preview-based action.
This action allows you to build and insert, or edit a selected, Markdown table using web-based tools which support preview, editing Markdown directly, or editing in a spreadsheet-style table editor.
If you cancel in the dialog, your changes are discarded. If you “Save Changes”, the updated table is inserted in the editor.
See video for demonstration:
This action likely has some room for improvement, if people have suggestions for tweaking it.
Get the example action from the Directory: