Logic Pro X keyboard command of the day. #LogicProX @StudioIntern1
Set Layout Tool 
Choose the “Layout Tool” in the “left-click” tool drop down (same place as pointer, solo, et al.)
The Layout Tool is what you use to change the position of a note in the score without affecting the actual time placement of the note. If you use the Pointer Tool to drag a note from 4 1 1 1 to the left to 3 1 1 1 the note will move, and apparently “replace” anything that used to be between 3 1 1 1 and 4 1 1 1.
If you use the Layout Tool to move the note left or right (no vertical movement is possible) the placement of the event in time will not change. You can move a note at 4 1 1 1 to the left to get it closer to the bar line, or to the right to get closer to the next note. Timing will not change.
It is best to use a MIDI loop and play with it in the Score Editor to get a feeling for what is possible.
Position items graphically in the Score Editor — Logic Pro X:
Using the Layout tool: The Layout tool is used to graphically move events in the Score Editor, in order to optimize the display without altering the timing of MIDI events.
⇧ SHIFT – ⌃ CONTROL – ⌥ OPTION – ⌘ COMMAND