I don't have
TablEdit, so I can't speak about the chord diagram feature, however, there is a free tab editor called
Powertab 1.7 that has that feature. Here is a link to the program and some TABs to play with and see if it works. When you install it, check out the menu of actions under Tab Symbols and you'll see
Pick Strokes and can choose Up and Down. It is also under the menu option
Rhy, Slashes. I haven't used this feature, though, so I don't know how well it works. It also has a Chord diagram list under
Guitar in the menu at the top. Again, I've never used it, so I don't know if it works.
I hope this helps.
Ray
Here is the link to download it.
http://acousticpower.com/index.html