I wish you had made it much simpler, in terms of actually how to use the mods people download on here. It can not be expected of everyone to understand these terms, as I certainly do not. I don't understand what $INT$ is, even from a google search, and I certainly did not see this alleged folder anywhere in any of the versions I downloaded. I could not use a single mod I downloaded, after spending about 2 hours looking for how to do it. The guides are of no help and neither are some of the replies. I am giving my rating because, while it may be a good loader, It is terrible in terms of user-friendliness so much so that I do not plan on touching it until I see a reply that gives a clear answer as to how to use the mods present within this community.
Adding mods is done the same way as without SDTL2. If you're new to SDT and don't want to fiddle around with files for hours (like I did), then I strongly recommend reading "Getting Started with SDT" ( https://www.undertow.club/threads/getting-started-with-sdt.7945/ ) as well as downloading a "Loader Bundle" (links can be found in the guide). You can use a Loader Bundle together with SDTL2 by replacing the "SDTL2/game" folder with the loader bundle folder (just make sure that the "SDT.swf" and "Loader.swf" files end up directly inside "SDTL2/game"!).
If you have any more questions you can post them on the forum thread (link is at the top of this resource's page)