1. Save/Load
It should be giving you a file save dialog, if it isn't please let me know. Because of the limitations you have to save somewhere else that isn't the same folder as the particle editor. Dumb I know, I even turned off sandbox mode. So I created a folder just beside the particle editor.
>>>> Taking a second look at it, I left out a function call in 1.4, so please download 1.4.1 to fix the file > save menu item.
2. Resize
I've been thinking of allowing this for sure. I can add it into my list of items to do
3. GitHub
I actually do have it on GitHub, just marked as private. Since I ask for a small donation for the source (currently) I would feel bad for accepting the PR and asking for a donation still. I know that GM is working on a particle editor (that will be interesting since I shared mine with them to fix some bugs) so when that happens I plan on taking away the donation ask and opening it all up. Hope that all makes sense, feel free to reach out on discord (Mickey#7321) or post in here