There's a known issue where Windows prevents SpriteMancer from saving to the app's root folder. Try a different one.
You can use Left Ctrl + LMB to change any slider into an input field.
You can use RMB on most sliders (there are exceptions) to revert the value of that slider to the default one.
While using the mouse wheel to change slider values, you can use SHIFT to move it at 10x the value and also ALT to move it at 0.1x the value.
We have sections in our Discord community for bug reports and suggestions. You can join it here: https://discord.gg/azdqRf8