I need to be sure that Hypersnap has a very important feature, before I purchase it...

I used to use this: https://addons.mozilla.org/en-US/firefox/addon/screengrab-fix-version/ for instantaneous, no scrolling necessary, full-page screenshots. It was fantastic.
But with a recent Firefox update, the addon broke, and it is now slow, forgets your last save location, and doesn't even work half the time.
Hypersnap LOOKS like it might be a good replacement, but I have concerns:
 
1. The (free) Firefox addon CAN instantly capture an entire page, (with watermarks) but it does NOT use the current ZOOM level. I often need to take screenshots that are zoomed in to 150%, even 200%. Does the paid version support this, or not?
 
2. The (free) desktop app (Hypersnap 8)(Windows 10) DOES use the browser's current zoom level, but the "Extended active Window" feature always ASKS me how large I would like the final capture to be... meaning that I have to guess exactly how tall the full webpage actually is, and then manually input that number. Surely, there should be a way for Hypersnap 8 to automatically know how tall a webpage is, if virtually scrolled all the way to the bottom. Does that functionality exist in the paid version?

 
3. If I purchase Hypersnap 8 (desktop version), will that also include a license for the fully functional Firefox addon?
 

But it is possible to use the browser's current zoom level. Screengrab! is still able to do it. You can download it and test it out yourself, if you don't believe me. It used to be an option, but now it's always on by default.
 
If Hypersnap 8 does not have this feature, I won't be able to purchase it. It's very important for me.

Well, looking at this page:
https://addons.mozilla.org/en-US/firefox/addon/screengrab-fix-version/versions/
 
I can see that the source code of Screengrab! is available under Mozilla Public License, version 2.0.
Could you look through it and figure out how they got the zoom level feature to work? I'm not suggesting that you copy the code outright. But I'm sure you'll be able to figure out what method they used.
 
Alternatively, if you can't get the Firefox zoom feature to work, could you get an auto-window-sizing feature to work on the Hypersnap 8 desktop app? Is there a way to determine exactly how tall a (fully scrolled) webpage is, rather than having to ask the user every time?

I wouldn't be so hasty!
I'm aware of that feature of Firefox. But it's also very slow to use.
https://stackoverflow.com/questions/13158083/take-a-full-page-screenshot-with-firefox
I don't see "take a screenshot" listed under the triple line menu.
You have to press SHIFT F2, then type in "screenshot -- fullpage" , and then the screenshot is saved... SOMEWHERE.
There are no options to choose where to save it by default,
No option to save in a different, user-defined location each time,
No option for what filename to use,
No option for auto-naming based upon a set of criteria (page name + date),
No option for image format,
and no keyboard shortcut to begin the entire process.
And finally, worst of all.... the method that they use for full page screenshots... doesn't always work.
 
That's why your add-on still has value... if it CAN do those things.
 
Screengrab! WAS able to do all of those things... but now that it's broken, I've been looking for an alternative...

I also have Firefox 58.0.2.
Maybe there is some setting deep down somewhere....
 

I maybe could estimate how tall the page is by using the extension code again, that is sending some message to my Firefox extension, waiting for its reply... A lot of work to implement this and frankly I don't see any real need for all this work. Using the built-in feature of FF you may either save a PNG to your downloads directory or copy it, then paste it into HyperSnap or any other graphics software and save where and how you want.

Actually i captured that page without any problems with built-in "Take a screenshot" feature of Firefox...
 
Or maybe not quite, looks like they have a limit of 10000 pixels vertical, it stopped there.