It's a feature called "Tracking" and processes your signal in 3D (X, Y, t) space, rather than standard 2D (X,Y) space.
The result is less noise grain, finer detail, more flexibility, and unique functionality. You will not find this in any other software.
StarTools monitors your signal and its noise component, per-pixel, throughout your processing (time). It sports image quality and unique functionality that far surpasses other software. Big claim? Let us back it up.
For its unique engine to function, StarTools needs to be able to make mathematical sense of your signal flow. That's why it's simply unable to perform "nonsensical" operations. This is great if you're a beginner and saves you from bad habits or sub-optimal decisions.
The Shrink module allows you to modify the appearance of stars in your image.
This guide lets you create starless linear data using StarNet++.
A brief tutorial on using Siril via the Sirilic front-end.
You may have to configure your operating system to not scale up StarTools.
You can convert everything you see to a format you find convenient. Give it a try!