Some options are:
There is Kindle Collection Manager (I didn't try that.) Here are some instructions. And here you can find the developer.
Calibre also has a Kindle Collection manager plugin, here is a howto, a semi-official forum.
I am guessing you have already found Amazon's Organizing Your Kindle Content. If every book on your devices is from Amazon, then you can do some organizing at 'Your Account' > 'Manage Your Device' > 'Your Kindle Library' or by using the cloud. If you have works from anyplace else, then the prospects get worse.
I personally have some OCD issues that ...
An alternative, which at least gets round "kindle is slow" is to use the Kindle app, on e.g. Android phone or tablet, if you have one, to manage your collections.
The Android app does support the new-style "cloud collections", as used by the PW, Voyage, etc.
The advantage here is that it is much more responsive, both in screen display and touchscreen ...
My own experience with this is that with Amazon you have a couple sets of collections. My iOS and android devices seem to share a set of collections that are automatically sync'ed across them.
In contrast my kindle device and my (mac) desktop software don't share the same. However, from my kindle device if I look at my "Cloud" items, then in the overall ...
I have tried many programs but all of them are still in the experimental stage.
Note that at this moment (Oct 2015) NO PROGRAM has support for Kindle v5.6 +. I contacted developers of KDEasy and they quickly answered:
So far we don't see any possibility to support 5.6, Amazon blocked all
the solutions. Sorry for that. Regards, KDeasy Product Manager ...
I think I see the problem (or one problem at least).
I have a massive set of collections on the kindle app for android. (Like 50 collections holding 2000 or more ebooks).
But when I install the Kindle for PC app for my Windows desktop, it does not let me import the organized collections from the Kindle app for android. When I use the Kindle for PC app, ...
BookFusion is what you are looking for. BookFusion provides you with a cloud based platform and native Android and iOS apps to allow you to easily upload , organize and read your eBooks across all devices.
More at https://www.bookfusion.com/reading/cloud-library
It is device agnostic and as a result you can read and access your books on any device. You ...
If you really need web reader to be part of solution (Google Play Books have web reader) - bookfusion is very likely answer you looking for. Web/Android/iOS.
Disadvantages: subscription (but earlier you lock in in early access one - better price you get). Library Interface/library management on mobile apps could be better. Vendor lock in (there is no ...
I use neat reader to sync and read epub books.
It has Android,win, Mac and web version and the iOS version would coming soon. You could import your books and read it everywhere.
New collections were not implemented on K4. Collections which you can create on K4 were created only on the local device. They won't go on the cloud.
According to the Amazon site, QUOTE: "Cloud Collections are currently supported on 6th Generation and newer Kindle e-readers, and 3rd Generation and newer Fire tablets." (and also, Kindle apps on Android/ios ...