First of all, I love the application, started using it recently and it's been really useful.

1 issue I stumbled upon is that for some reason, when you take a screenshot (and it's copied to your clipboard, either automatically or by pressing Ctrl + C on an existing one), if you try to paste it into WhatsApp(the Desktop app) to send it to someone, it doesn't really work. It somehow recognizes that an image was "pasted" but it just looks "blank", and if you try to hit the send button nothing really happens happens.
Like this:

Don't know if the issue is more with WhatsApp, but that doesn't happen when using the built-in windows snipping tool, or when copying a random image or image segment from the web or Paint.
If I paste the screenshot from ksnip into Paint, and try to copy it from there, it works just fine.

Apart from that, I have a few suggestions that I think aren't too hard to implement, and that would be quite useful.

1 - A colour picker tool.
So that we can sample a specific point and get its RGB/HEX value directly.

2 - A ruler that doesn't rely on taking a screenshot. Currently (to my knowledge) we can visualize/measure it but only when taking the screenshot, there's no way to do it within the program's interface, to a captured image.

3 - The possibility of navigating between tabs using shortcuts.
As can usually be done in Web browsers or Photoshop, using "Ctrl + Tab" & "Ctrl + Shift + Tab".