Hi eishiya, I'll go point by point.
- Set a delay on particle emission
- This is actually on our roadmap, It was in the low priority queue but I've just moved it to high for being a high requested feature. It should be added in the next update.
- Have slower speeds
- You can just right click any slider to input any value, even if the value is not between the default min/max values.
- Adjust the values of sliders with the keyboard
- That's a nice idea, you can adjust the values with the mouse wheel, but I'll add the arrow keys and WASD for my gamers fellows.
- Control the frame rate
- Yeah, it was removed with the UI rework, we forgot about it :P. We'll add it again in the next update.
- Copy+paste emitters
- As you said, this is now a feature that will come in the next update.
Thanks for all the suggestions!