I find the infill level slider an obvious, but not well enough thought out implementation of the need for adjusting the infill.
First of all, no one needs to be able to choose between 100 or more different levels of infill. No idea how many steps the GUI slider element actually has, but adjustment in 5% steps should be enough and are much easier – and that is the actually important point – to replicate (= make the exact same settings at any later time).
Second, the slider should be non-linear. To give you a (reversed) example: I drive a Lotus Elise, and the 0-3K range on the speedometer is compressed, cause that's the range no one cares about when properly driving that car:

I find the infill level slider an obvious, but not well enough thought out implementation of the need for adjusting the infill.
First of all, no one needs to be able to choose between 100 or more different levels of infill. No idea how many steps the GUI slider element actually has, but adjustment in 5% steps should be enough and are much easier – and that is the actually important point – to replicate (= make the exact same settings at any later time).
Second, the slider should be non-linear. To give you a (reversed) example: I drive a Lotus Elise, and the 0-3K range on the speedometer is compressed, cause that's the range no one cares about when properly driving that car: