Is there a way to drag and drop a single image from a Windows folder into a catalogue quickly?

Lightroom and GIMP are completely different applications with different purposes. Photoshop works the same as GIMP, since it is a pixel editing application and not a digital asset manager/organizer.

The intention is that you import everything into Lightroom, use that to organize, and do editing in Photoshop or another pixel editor. Lightroom does not have anywhere near the range of tools that you would find in GIMP or Photoshop.

If you really do not want to use the Lightroom paradigm (of an accumulated image library) but prefer to treat digital photo files individually, essentially the same image editing tools are available within the Adobe Camera Raw input filter for Photoshop. For example: applying preset looks or manual adjustment, global and localised, with some limited retouching. PS is already configured so that whenever a Raw file is opened, the ACR window pops up and then you can apply parametric editing onto this. This editing is then saved back to the file (unless you Cancel out) by the Done button so that it will still be there when you return to the same image. Alternatively it is saved out plus the image is brought into PS itself, if you click Open.

Optionally PS settings for ACR can be configured so that the same thing will also happen for different image file types besides Raw. ACR provides "snapshots" so that multiple parametric treatments all referring back to the same source file can be named, saved and then later recalled. It's all a bit clunkier and less fluid IMO than the LRc interface but technically the end result can be pretty much the same. Just, be aware that outputting results of editing is likely to be found a lot less efficient. 

This environment does lack a lot of the bulk management, virtual organisation, editing and output facilities that (any variant of) Lightroom provides, but if only considering images one-by-one and manually, those things will scarcely apply anyway. 

A suitable front-end for navigating and managing images under this workflow, and opening them up for editing, might be Adobe Bridge or some other equivalent. Effectively Adobe offers two paradigms: library based and file based. We need to be clear-eyed about whichever is the best fit for us. Unfamiliarity, though, has little to do with that choice.

Initial experience of Lightroom often involves some - perhaps quite unsettling - UN-learning of rules of thumb that may previously have gone unquestioned. Only then can the value of the library based approach be appreciated and profited from. There is some mental threshold to get over, in other words. But this is not to say everyone must prefer life on the other side of this! This forum is made up of those converts by and large.

You cannot bypass the Import screen in Lightroom Classic. You would be better off dragging and dropping many photos at once, instead of one at a time. Essentially doing it one photo at a time is not really the way LrC was designed to work, and thus not optimal.

If you keep thousands of photos in a single folder (in other word, not in subfolders), this process will be slow.