Thanks @Eduardo ! Appreciate the feedback.
Good idea, thanks! I'll add this command to a menu in the next release. For now, there is already a registered command called "Toggle Time Slip panel" that you can access using Cmd/Ctrl+Shift+P.
EDIT: Released v0.2.1 with the command added to the View menu.
I understand the appeal of a Markdown table. I'll explain the design decision to use CSV. I'd argue that CSV to data tables is like Markdown to notes. There is no need to export a note (in the sense that it requires processing or formatting) for the information to be accessible anywhere else. At the same time, it is also human readable and editable, even though many users prefer Rich Text editing to raw Markdown editing. CSV is similar in that sense (at the very least, this is probably the most standard text-based format). Therefore, in this specific context, I see a Markdown table as an export, or rather rendering, of the CSV and not the other way around. 
Given that CSV is the native format, and Markdown is the rendered output, I see two possible approaches. The first is already available in Joplin in the form of the Paste Special Plugin. Essentially you can render any CSV, including Time Slip notes, as Markdown tables automatically (see video below). The second, is to have a Markdown-it plugin that renders CSV as a table in the preview pane.
As there is already an implemented solution for this I see this as out of scope for the plugin, but I may change my mind. It's still very new. 
