we have had this request a number of times, it is in our feature database, but I don't know when it might be implemented.
Do you use the tap and hold feature with the sliders. If you tap and hold on either side of a slider it will start to move slowly so that you have the ability to get to a more exact number.
Also, I find that using a stylus helps with accuracy on sliders.
I've just started to use LumaFusion, and ran across this same problem. I agree it would be very helpful to be able to type a value in.
I was trying to set a frequency in an audio filter, and could not get closer than about 30 hz, It goes up by 1/100th of a hz, so Press and Hold is really slow.
Maybe as a quick improvement, it could go up/down faster the longer you hold (i.e. similar to many other devices, like clock radios).