The uploader that's built into jAlbum does exactly that - it uploads only new or changed files and folders. If you're using another FTP client program, like FileZilla, you can tell it to do the same thing.
Trying to do this manually is usually a bad idea. You might think that only some files need to be uploaded, but there are often others that must also be uploaded. Trying to figure that out on your own often doesn't work, and you end up with a broken album on your server.
If you're using one of the skins that uses JSON database files, the album build process has to reconstruct the main database. There's no clever way to avoid that, and it can take a bit of time.
With other skins, there shouldn't be any long waits. I've got a couple of large-ish albums (not 100k images - who's looking at all those?), and using my own skins, I can add a few images, click Make Album, and be done in less than 10 seconds.
In either case, however, jAlbum does not reprocess images it doesn't need to, and that's where the bulk of the album creation time is (especially with videos). So, when you're just adding a few things, the album build shouldn't be anywhere near as long as the initial build.
Because some skins may not scale up very well, you might want to consider not keeping everything in one massive project. It might be more efficient to create an "album of albums," with links to a collection of other, independent projects.
The downside to that is that you lose the ability to provide things like a search function that spans all of the material, or to provide a large, cascading menu at the top.
I'm puzzled about the problem you're running into. Adding material to a Tiger album might not be quite as fast as adding material to an album made with another skin, but it should still be fairly speedy, unless you're pushing an aging, under-powered laptop to its limits, or running on a slow, external drive.
Can you describe the scenario? How many objects and folders are in the project? When you add a few things and hit Make Album, how long does it take to finish?
You're not doing something like choosing Force Remake, are you?
I've already made 20 folders. I plan to upload a lot more. Check my profile https://vi3w.jalbum.net/
I sort them by date. The time to upload depends on how many new photos I upload. For now it's ok. But what if I already have 1000 folders with about 200,000 photos. My archive is about 1M photos.
No I haven't used Force Remake
You're using the album search function, the tag cloud, and a cascading top menu. What that all means is that the archive really does need to be one large project. And those features also pretty much require a JSON-driven album, like Tiger.
I have no idea how that will all scale up to a million-image project. All I know is that following a skin update, for example, updating the entire project is going to take some time. There's no magic.
If you sort a huge album project by camera date, then you can speed up the process by changing the sorting order to "Custom". Just open a folder within jAlbum and rearrange two thumbnails back and forth to change the ordering to "Custom" without actually reordering the objects (i.e. they're now still in camera date order, but jAlbum now uses a small lookup-file to do the ordering instead of opening each image file and checking out the camera date.)