PicSender is a stand alone G-code sender with strong support on this and other forums. It runs extremely long G-code files that UGCS can’t.
It is a paid option (About $30 USD). Customer support is quick and it is kept up to date as new features become available.
For quick one of a kind jobs I use (UGCS - version 1.0.9 [the latest stable build]) and for bigger jobs I use PicSender.
PicSender is integrated with grbl 1.0c (laser enabled and recommended along with spindle work) and 1.1f/g - not recommended for laser but supports spindle work.
I did work with John and Jeff when optimizing my grbl build.