Hi.
Here is a script that does what you need.
Probably k will give you a most efficient way of doing this, but, for now, I think it can help you.
Feel free to improve it in any way desired.
UPDATE (03/23/2023):
I didn't review the code. Just grabbed it from another folder I have in Google Drive.
var defaultValue = "3";
var space = prompt("Type the pyramid edge width.", defaultValue);
var doc = fl.getDocumentDOM();
var timeline = fl.getDocumentDOM().getTimeline();
var selectedLayers = timeline.getSelectedLayers();
var count;
var increment;
function start()
{
if (!doc || !selectedLayers || selectedLayers.length == 1 || space == null)
return;
else
{
space = space.replace(/\s/g,'');
if (isNaN(parseFloat(space)) || space <= 0)
return;
else
count = Number(space);
increment = count;
}
for (var i = selectedLayers.length - 1; i >= 0; i--)
{
timeline.setSelectedLayers(selectedLayers[i], true);
timeline.insertFrames(count, false, 0);
timeline.insertKeyframe(count - (increment - 1));
count += increment;
}
}
start();
-----------------------------------------------------------------------------------------------------------------------
JSFL download: layers_pyramid.jsfl - Google Drive
Usage:
Select the layers you want, type in the value of the pyramid's edges or leave the default and press 'OK'.
Code (for reference):
var defaultValue = "3";
var space = prompt("Type the pyramid edge width.", defaultValue);
var doc = fl.getDocumentDOM();
var timeline = fl.getDocumentDOM().getTimeline();
var selectedLayers = timeline.getSelectedLayers();
var count;
var increment;
function start()
{
if (!doc || !selectedLayers || selectedLayers.length == 1 || space == null)
return;
else
{
space = space.replace(/\s/g,'');
if (isNaN(parseFloat(space)) || space <= 0)
return;
else
count = Number(space);
increment = count;
}
for (var i = selectedLayers.length - 1; i >= 0; i--)
{
timeline.setSelectedLayers(selectedLayers, true);
timeline.insertFrames(count, false, 0);
timeline.insertKeyframe(count - (increment - 1));
count += increment;
}
}
start();
Demonstration:

I hope it helps.
Regards,
JC