My understanding of MOGRTs is that, while both are used in Essential Graphics, the ones created in AE are different from the ones created in PP. I know you can open a MOGRT in AE, edit it and resave it, but I'm pretty sure once it's in Essential Graphics in Premiere, it's wrapped up.
As for adjusting leading in your MOGRT, you might try adding the Increase Tracking effect to your text layer, delete all keyframes, then add a Slider Control and parent the Tracking Amount to the Slider. That Slider can now be added to your controls in Essential Graphics.
o2 ideas - Birmingham, AL
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