I use a regular line drawn straight (horz) from the lower right corner of the last character in a table column 1 (or mtext column 1) to the lower left of the first character in the adjacent cell (again..."or mtext column").
Now set the properties...
Change the linetype to Dot
Set the lineweight to at least 1.00MM
Set the color to what you want...
Copy the line down vertically using the Copy...Array (for the number of rows you need).
Finally you can stretch one or more lines at a time to align the left side to your text right after editing that line.
You may need to check the colors in you text background you can use the whiteout color for the text background.
Be sure when you plot you use those lineweights!
It may sound like a lot, but in a CAD guys day...these steps are nothing special...just the daily grind. I process my drawing index tables this way.
If you really want to automate this task I would start with the (textbox) function to obtain the typed width of the characters you typed and adjust the line automatically with a single line of lisp code entered at the command prompt that would adjust the end point of the left end of the line for you.
One more layer of automation would monitor the table and/or mtext via a lisp reactor to update the dot leader tab lines after you have changed the table/mtext object.
There are several ways to perform this tack using a number of objects.
Over the years I have used an xref "blanket 'o' leader dots" with a xrefclip to handle the changing number of dots
required for each line....,
a single-line array of donuts (yes it is still a command in autocad) so I could use grips to change the number of dots numerically via the properties tab.
At the end of the day...I believe this functionality should have been included when tables were first introduced into Autocad...I would have.
HTH.Rob