Creating .mogrt with adjustable keyframes for Premiere

I was able to create a workaround. It's not entirely pretty on the AfterEffects end, but it makes it easy for the Premiere editors.

The lower third is a graphic that animates in from right to left. Longer titles require it to animate further to the left than short ones.

I created a null object on Layer 1 with a slider control.

For the position of the lower thirds graphic, I used this expression:

t0 = inPoint;  

transitionDur = 2;  

holdDur = 5;  

// A, B : start/end value for the x coordinate  

//A = initial position before animation

A = (2588)

B = thisComp.layer("Null 1").effect("Slider Control")(1).value; 

//C = 50; 

C = 2588;

y = value[1];                // or some constant numeric value like 0  

t1 = t0+transitionDur;  

t2 = t1+holdDur;  

t3 = t2+transitionDur;  

x = (time<=t1) ? linear(time, t0, t1, A, B) : linear(time, t2, t3, B, C);  

[x,y]; 

The Source Text for the Lower Third and the Slider Control for the Null Object go in the Essential Graphics panel. Export that as .mogrt and you have simple controls for Premiere with animations intact.

Credit to Adding Keyframes to Sliders in Essential Graphics where others were having a similar problem, and Advanced expression (position) question  where UQg wrote the expression I ripped off and tweaked the variables for my own comp. Thank you!