Quick Answer: The LN Live Scale Selector allows you to set a scale for playing with a QWERTY computer keyboard when NOT in mode Play (i.e. Stop).
Note: This feature has been (re)moved in version 1.5.3 of Liquid Notes. Only the Current Scale of your arrangement is shown in that window. The LN Live Scale Selector has been moved to Settings > General.
LN Live Scale Selector in Liquid Notes
At the bottom right of the Liquid Notes window the LN Live Scale Selector can be found. It has a double function: when a song is playing, the Current Scale of your arrangement at the position of the cursor (playback head) is shown. Any change in the scale of your song will be indicated there as soon as the cursor hits the chord introducing that scale change.When not playing back a song, i.e. being in mode Stop, you may set any scale from a drop-down menu to 'improvise' with a QWERTY computer keyboard or MIDI device (e.g. keyboard) to hear the notes in this respective scale.
As soon as you hit Play only the Current Scale of your song will be shown again, and any input from the drop-down menu is disregarded.