[Walter Soyka]

I agree with Arie; there are some nice tools in the market already to support you here without you having to learn scripting. CompsFromSpreadsheets is another option:

https://aescripts.com/compsfromspreadsheet/

One big note, though, if you do decide to write your own script, it’s Javascript, not Python! There are a few good resources here:

https://motionarray.com/learn/after-effects/places-to-learn-after-effects-scripting-online/

[Walter Soyka]

I use Flow a lot for easing:
https://aescripts.com/flow/

This lets you use CSS-style curves, which you could document as such. You could even share the curve presets directly with other artists.

[Walter Soyka]

Try clearing your cache.

Edit > Purge > All memory and disk cache

[Walter Soyka]

You can control the Size parameters via sliders that you expose to Premiere, too!

How do you want the controls to appear in Premiere Pro, and what do you want them to do?

[Walter Soyka]

They’re all still images, right?

I’d put them all in one source comp, trim them all to a single frame in duration, and use Sequence Layers so each frame of the comp shows one of the images.

Back in your main comp, I’d use however many copies of that source comp layer as I needed with time-remapping enabled and each layer referring to a different frame.

[Walter Soyka]

This reference is almost out-of-the-box with Plexus:
https://aescripts.com/plexus/

[Walter Soyka]

The current release of Ae can open CS5.5 files no problem — I just tried to make sure. I think it can even go back a couple of releases beyond that. Ae’s backwards compatibility is pretty good.

Forward compatibility is a different story, though. Ae will require you to save the project file in the current AEP format after you open it, and only this version or newer will be able to read that. You can manually save back 2 versions in Ae — and you have to do that explicitly via Save As — so you will not be able to open your new, updated files in CS5.5.

[Walter Soyka]

Ae doesn’t work that way. You have to import your image into the project (kind of like a linked file in InDesign), and then you can bring the image from the project into the composition as a footage layer.

If you need a good starting point for learning Ae, you could try this link:
https://helpx.adobe.com/after-effects/tutorials.html

[Walter Soyka]

Your screenshot didn’t attach; maybe you can repost if this doesn’t help.

To edit a slider’s range in either the Effects Control Panel or the Timeline, you have to right-click on the “Slider” text and select “Edit value.” The range is listed in there.

To edit a slider’s range in the Essential Graphics panel, just click the “Edit Range” text to the right of the slider. If you don’t see it, try dragging the panel wider in your UI to reveal the control.

[Walter Soyka]

Don’t forget semi-colons to end your statements.

I modified your code a bit. Here’s how I’d get those vertices:

var project = app.project;
var currentComp = project.activeItem;
var selectedLayers = currentComp.selectedLayers;
var myLayer = selectedLayers[0];
var layerIn = myLayer.inPoint;
var layerOut = myLayer.outPoint;
var maskPathProp = myLayer.mask("Mask 1").maskPath;
var vertices1 = maskPathProp.keyValue(1).vertices;
var vertices2 = maskPathProp.keyValue(2).vertices;
alert(vertices1);
alert(vertices2);