First off, thank you very much for this plug-in. I find it very useful!
Would it be possible to add the ability to run an external program (such as a shell script) on save? I have a script that trims trailing whitespace and coverts tabs to spaces (might be introduced by other contributors). It would be great if I could run this script whenever I save a Lua file. I did some googling and the only other way to accomplish this is to define a builder that run the script. However, that's less than ideal because it's a more complicated solution.
It seems your real need is to clean your code on save (convert spaces-tabs, remove white space ...)
If you want to do that there is a plugin which does this kind of stuff, I never test it with LDT but I suppose it works. If you want to test it : http://andrei.gmxhome.de/anyedit/
For action on save, I don't know an other solution than add a builder on your project. It's a bit complicated but this is a generic feature available for all 'eclipse project'.
The documentation to add a builder is here.
But we think about that when we will plan the next features .