Pausing before a print

I am trying to set up a way for me to be able to pause the print immediately before it starts the first layer so I can raise the z-axis and then lower it again. Essentially I am using Marlin and trying to place an object directly under the nozzle once it begins, but I need a way to pause each print to find where it will begin and add the object. I am a little new to slic3r, but I was wondering if there was a way I could enter anything into the Printer Settings->Custom G-code -> Start G-code section or if I will need to go into each G-code and edit them. Thank you for any help.

Start gcode ends before the nozzle moves to the point where it will begin extruding. To avoid editing each file manually you'll need a post-processing script...But a pretty easy one.

RepRapFirmware provides M226 (Gcode initiated pause) for this and similar purposes, but Marlin appears to have allocated this code to 'Wait for pin state' instead. I guess you could use it with Marlin if you hooked up a push button to a spare pin.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Not sure I follow what you need to achieve. The first move will be to the start position of the skirt (or perimeter of the print if you have no skirt), so a pause before the skirt or perimeter has printed will not put the nozzle over a known place on the printed part. You will know where you placed the print on the bed in the slicer (usually the centre), so surely you could just place the object on that part of the bed before the print starts?

Dave