[tomsem]

I can confirm that only side loaded KFX gives you 2 column option. This is a little silly, since the Kindle apps give you 2 column option for any of the reflow-able formats they support.

But KFX is the order of the day, and Kindle devices have never had 2 column support prior to this, so it's not a regression. But it is awkward when you have a 2 column theme in effect, and happen to load a format that doesn't support it: you need to change the layout to read it, then change it back to 2 column mode for the supported content.

Of course, they could add support for legacy formats later (do not hold your breath).

I am happy with the way KFX looks, so it's not an issue for me. Rather, it is that the 'other' books (a small percentage of what is in my library) don't look as good to me.

If I were side loading a lot, I would get something other than a Kindle. My Pocketbook Era is a nice device for this, and very friendly to side loaded content, and if you like koreader, it is dead simple to install it. It also will upload the side loaded content to cloud and the mobile apps are not bad. It pays attention to series and tag metadata, etc.

I am enjoying 2 column mode, but then I'm a sucker for trying out new features. Will have to see if it sticks with me.

For some reason I have never liked to use 2 column mode on tablets. When I use Kindle app on my iPad Pro 12.9, I use Stage Manager to control the app window proportions and size so it's more comfortable in portrait and landscape. And on smaller iPads I have been know to use Split Screen to reduce the app window so it isn't so wide in landscape.

I fired up my old Windows computer to see if Word had Send To Kindle Share option: not yet, for me (I do have MS 365 subscription). Based on how Share works without this option, it doesn't look like you'll be able to do it without 1) saving to OneDrive and 2) sending it to some Send To Kindle API. I don't think I have any use for it, but am curious to learn more about how it works, so will be checking (I just installed Office today on that machine and it has some other updates so maybe it'll show up soon).