Is there a way to open to the current IDE line number or cursor position?
If the external editor allows setting them in the command line, then yes, using the macros
$Col() and
$Row().
Following on the example above for leafpad you would just set the parameters to:
--jump=$Row()
$EdFile()
Note that if the file on disk is different than the one in the IDE (i.e. if it's modified) you have to save it first by adding $Save() to the parameters like this:
--jump=$Row()
$EdFile()
$Save()
As yo can see in the image, there is a full list of macros in the "Add tool" window. Play with them to see their effects