GTKWave is no longer required!
We want VHDPlus IDE to be a all in one Tool for all FPGA Programming needs. Since GTKWave was not reliable on some platforms, we decided to create our own VCD viewer.
The VCDViewer in it's current state works with great performance.
Still, there are some features missing that will we added with the next updates.
If you prefer GTKWave, it is still possible to use it by setting the option Use GTKWave located in Extras -> Settings -> Simulator