As it currently stands, it seems there is no way to granularly max or zero out an individual reagent quality input while in Simulation Mode, like you can with all reagents at once with the quality icon buttons at the top of of the window.

My current workflow is to use the top quality buttons to max out all reagents to one quality, and then click into each individual cell (as pressing the Tab key does not move into the next cell, as a Browser would), type 0, then click into another cell, and type out the maximum value, which ends up being quite tedious.

Two potential solutions:

1. Shift + Click on either the + or - icons could bring the simulated reagents to max or zero for that individual quality, respectively
2. Individual quality maxxing buttons on a per-reagent granular scale, similar to the all-reagent button at the top of the Sim Mode UI