Managed to fin a solution for this little problem I had (Failed to start game (missing executable)), when first installing the new workshop tools.
- Opt in for Steam beta, this is done by going into "Steam" (top left corner in steam) -> "Settings" and then in the "Account" tab opt in for the Steam Beta.
- Restart Steam
- Force a Dota 2 update by right clicking on Dota 2 in yo u installed games list, then "Properties", and under the "Local Files" tab click the "Verify Integrity of Game Cache"
- Wait for the 5.5 GB download to complete.
- Go to "Library" and select "Tools", then install "Dota 2 Workshop Tools Alpha"
This solved the problem for me on Linux at least, I do not know if this works for Windows and OS X users, but I reckon that this solution should work for you as well if you use Windows or OS X.