I can’t tell if TeraCopy’s write cache is the same entity to ExtremeCopy’s buffer from that screenshot only.

The thing I get instead is that TeraCopy has the ability to integrate into Total Commander and Directory Opus by adding a button on taskbar. I know developer of those file manager provide SDK kit for third party developers. Chances are TeraCopy made use of that path. Easersoft did not make ExtremeCopy work like that in other hand. But XYplorer users probably are able to produce this by themself.

It seemed a few users here are XYplorer users. While XYplorer does not offer SDK, there is Scripting feature by which it is possible to put ExtremeCopy and XYplorer in conjunction. Upon editing script for FastCopy and TeraCopy , may be we can replace XYcopy with ExtremeCopy. During test, i discovered XYcopy does not resume a paused copy task from the point it stopped but from beginning.