Regarding item 1 you can take a look here:
I requested the same some time ago.
On Sat, Oct 3, 2015 at 2:05 PM, Женя Петкевич (Gene Petkevich)
> Hi all,
> I wonder how is possible to configure Zim to support High DPI screens? I
> currently have one, and most of stuff is working correctly except for the
> following things:
> 1) checkboxes are very small and barely visible
> 2) other icons are very small too
> 3) dialog boxes (like adding link) are too small by default (after each
> restart I resize them again and again)
> 4) arrows in the left pane are barely visible and indentation there is very
> 5) tabs in the content are are too small too
> Item 5) can be easily fixed by changing pixel indentation constant in
> Item 1) is very important to me and I have tried to replace images of
> checkboxes with bigger onen, but that didn't change anything.
> For me Items 1) and 4) are the most important.
> So I wonder if there any easy fixes for now to cope with that? And also
> regarding changes in code, is it possible to change without breaking the
> program architecture? I would be happy to contribute to Zim.
> Best regards,
> Eugene Petkevich
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