The controls for adjusting things like opacity, shrink size etc do not register user input until the user has tried to drag them a minimum distance. This has the effect that it is impossible to easily adjust the value by a couple of points, instead jumping and then having to move back. Additionally if the value is low, it's impossible to reduce the value except by dragging to the right and then back left, if the control is near the left edge of the screen. Maybe removing these controls in favor of a pop-out editor with text-entry + up/down increments would be an improvement? Or just add incremental-change buttons alongside?(except in cases where the slider control is particularly appropriate)
Part way fix done in 5bd70bd79d0eb3aa669a0c071e4c073a591b62da More work is needed as precision interaction suggested is still not sorted. This is less high priority than the initial fix though, so reprioritising to low.
As this item is now no longer a functional issue and more some suggestions for some interaction help.