I'm using IdeaMaker for slicing my print objects. IdeaMaker start strings have a >T0< standing alone on one line and then >T1< on the next line. What does this accomplish?
T stands for "Tool" and has its origin in the origins of
.gcode being for other automated machine controls. Depending on the machine, everything could be a tool for
.gcode, like an actuator or pump or a spindle motor or a drill.
In 3D printers, the T-controlled tool is usually the extruder motor. Convention has it that the indexing always starts at 0, so T0 and T1 are your first and second Extruder respectively. It is the way to choose which tool is used.
As a side note: E is not originally intended for extruders but for the feed rate of lathes.
I'm not sure what it's doing in your case, but the "T" code is there to select the extruder number. T0 would be the first and T1 would be the second extruder in a multi-extruder setup. I found the information at the end of this cheat sheet.