As mentioned in the below comment in another thread,
and according to the Transforms module documentation regarding editing:
Note: Linear transform edit sliders only show relative translation and rotation because a transformation can be achieved using many different series of transforms. To make this clear to users, only one transform slider can be non-zero at a time (all previously modified sliders are reset to 0 when a slider is moved). The only exception is translation sliders in “translate first” mode (i.e., when translation in global/local coordinate system button is not depressed): in this case there is a only one way how a specific translation can be achieved, therefore transform sliders are not reset to 0.
there should only be one slider with a non-zero position at a time. However, using latest stable Slicer 5.2.1, I’m observing that I can cause more than 1 slider to be non-zero. Moving the sliders will reset the other, but if I insert in the rotation with the spinbox, that resetting behavior seems to no longer work. Is this a bug?
Related threads on transform sliders behavior: