Premiere Pro Scripting ExtendScript question

I was able to make something work. Basically you're right, there is no "Cut" or "Add Edit" function available in ExtendScript. Why? I have no idea, since Premiere is an editing program, you think Adobe would make this available, since the "Add Edit" function is under Sequence > Add Edit (Control + K).

So, here is a very basic and heavily commented small piece of code. It just performs a cut at the playhead time, or performs multiple cuts based on a collection of time objects.

Please feel free to read out to me if you have any questions.

// PSUDO-PROGRAMMING CODE STEPS I TOOK JUST TO MAKE A CUT USING EXTENTSCRIPT IN PREMIERE PRO
// 0. get the project item reference from selected clip, clip.projectItem
// 1. get video track that the clip is on
// 2. get the play head position, just incase you want to visualize the cuts being made
// 3. calculate the time of the clip the playhead is over, that will be the in point, and get the out point
// 4. set the project item in point and out point, for video, audio, or all
// 5. insert the clip onto the track at the playhead position track.overwriteClip();
// 6. deselect the track to avoid any issues

function main(cutPositions)
{
    var activeSequence = app.project.activeSequence;
    if(activeSequence)
    {
        // get selection of track items
        var trackItems = activeSequence.getSelection();
        if(trackItems.length > 0)
        {
            // CAVEAT: linked video and audio track items on the same track,
            // example: track item on Video 1 and Audio 1, video track item will appear first in the array.
            // however, if video track is on Video 2 and audio track is on Audio 1, audio track item will appear first element in array.

            // ARE YOU LOOKING AT ONLY CUTTING VIDEO TRACKS OR AUDIO TRACKS?
            // get track item type you want to reference in your selection of track items.
            var mediaType = 'Video'; // or 'Audio'
            var tracks = (mediaType == 'Video') ? activeSequence.videoTracks : activeSequence.audioTracks;

            // remove the track items from the selection you don't want to process                
            for(var i = 0; i < trackItems.length; i++)
            {
                var trackItem = trackItems[i];
                // we will use the "mediaType" STRING, instead of the "type" INT
                // trackItem.mediaType == "Video" or trackItem.mediaType == "Audio"
                // INSEAD OF
                // trackItem.type == 1 or trackItem.type == 2

                // if track item is not the media type you initialized above, then remove it from the array
                if(trackItem.mediaType != mediaType)
                {
                    trackItems.splice(trackItems.indexOf(trackItem), 1);
                }
            }

            // loop over all the track items in the new array and do cuts
            for(var i = 0; i < trackItems.length; i++)
            {  
                // USE THIS VARIABLE TO PASS INTO OTHER FUNCTIONS TO REFERENCE THE CURRENT TRACK ITEM BEING WORKED ON
                var trackItem = trackItems[i];
                
                for(var j = 0; j < tracks.length; j++)
                {
                    var track = tracks[j];
                    var clips = track.clips;
                    for(var k = 0; k < clips.length; k++)
                    {
                        if(clips[k].name == trackItem.name)
                        {
                            trackItem.track = track; // used to store the track that our track item is on
                        }
                    }
                }
            
                // just check if the track item is on a track, which it should be, if not do nothing
                if(trackItem.track == null) return;

                // THIS PART IS SUPER IMPORTANT, ADDING 2 TIME OBJECTS TO THE TRACK ITEM FOR REFERENCE LATER
                // get the sequence time of the playhead
                trackItem.sequencePlayheadPosition = activeSequence.getPlayerPosition();
                // get the track item time of the playhead
                trackItem.playheadPosition = new Time();
                trackItem.playheadPosition.seconds = trackItem.sequencePlayheadPosition.seconds - trackItem.start.seconds + trackItem.inPoint.seconds;

                if(cutPositions)
                {
                    // THIS IS PROBABLY WHAT MOST PEOPLE WANT TO DO
                    cutFromTimeArray(trackItem, cutPositions)
                }
                else
                {
                    // JUST A BASIC CUT AT THE CURRENT PLAYHEAD POSITION
                    cutFromPlayhead(trackItem);
                }
                // deselect the everything and update the UI
                var itemsToDeselect = activeSequence.getSelection();
                for(var i = 0; i < itemsToDeselect.length; i++)
                {
                    itemsToDeselect[i].setSelected(0, 1);
                }
            }
        }
        else
        {
            alert("Please select a track item (clip) on the timeline");
        }
    }    
}

function cutFromPlayhead(trackItem)
{
    // get project item of the selected clip
    var projectItem = trackItem.projectItem;
    
    // perform cut at playhead position
    projectItem.setInPoint(trackItem.inPoint.ticks, 4);
    projectItem.setOutPoint(trackItem.playheadPosition.ticks, 4);
    trackItem.track.overwriteClip(projectItem, trackItem.start.ticks);
}

function cutFromTimeArray(trackItem, cutPositions)
{
    // get project item of the selected clip
    var projectItem = trackItem.projectItem;
    
    for(var cut = 0; cut < cutPositions.length; cut++)
    {
        // get the sequence time of the cut
        var cutPosition = cutPositions[cut];
        // move playhead to the cut position
        app.project.activeSequence.setPlayerPosition(cutPosition.ticks);
        
        if(cutPosition.seconds <= trackItem.start.seconds || cutPosition.seconds >= trackItem.end.seconds)
        {
            continue;
        }
        else
        {
            // get track item time of the cut position in the sequence
            var playheadPosition = new Time();
            playheadPosition.seconds = cutPosition.seconds - trackItem.start.seconds + trackItem.inPoint.seconds;

            projectItem.setInPoint(trackItem.inPoint.ticks, 4); // 1 for video, 2 for audio, 4 for all
            projectItem.setOutPoint(playheadPosition.ticks, 4); // 1 for video, 2 for audio, 4 for all
            trackItem.track.overwriteClip(projectItem, trackItem.start.ticks);
        }
    }
}

// PLEASE COMMENT/UNCOMMENT THE MAIN FUNCTION.
// USE ONE AT A TIME, SINCE EVERYTIME IT IS RUN, IT DESELECTS EVERYTHING

// DO SINGLE CUT AT PLAYHEAD POSITION
var cutPositions = []
cutPositions.push(app.project.activeSequence.getPlayerPosition());
main(cutPositions);

// OR

// MULTI-CUT, MAKE AN ARRAY OF TIME OBJECTS
// in my example, I made 3 cuts, one at the playhead time, the others 1 and 2 seconds after playhead time
var cutPositions = [];
var cut1 = app.project.activeSequence.getPlayerPosition();
cut1.seconds = cut1.seconds + 1; // first cut 1 second after playhead
var cut2 = new Time();
cut2.seconds = cut1.seconds + 1; // 1 second ahead of the first cut
var cut3 = new Time();
cut3.seconds = cut2.seconds + 1; // 1 second ahead of the second cut
cutPositions.push(cut1, cut2, cut3); // put all the cut times (based on sequence/playhead time) into an array
//main(cutPositions);

>why can't I script making a cut on the timeline?

Because ExtendScript can already add, remove, and change any trackItem.

I'm struggling to see how this is a "HUGE issue"; perhaps walk us through the entire workflow you'd like to support, from the user's perspective, and we can provide better guidance.