The documentation for creating custom toolbar items may be improved. There are some examples in the source code, but only for hg commands (eg update) or external commands, not for tortoisehg/workbench items. I wanted to add a button for the shelve, after searching a lot, not finding anything, I tried "thgw shelve" as command, just a guess. Finally it worked. This should be documented. If you see the sourcecode, the command for the shelve in the menu is just "shelve" but that does not work on the custom toolbar: "cannot find file" error. Maybe this could be supported on the custom toolbar as well or else the documentation could be improved. (PS: in the docs it is mentioned that the shelve can be started with "thg shelve", but there is no doc about the custom toolbar, where I searched for actually; further "thgw" is needed to about a dos box in windows).