Hello,
I have to work with icons for folder/file names and unfortunately the correct display of these Unicode icons does not work properly, e.g. with this: 
, this is displayed:
.
Therefore I would like to install an extended font for an AppVM, but I don’t know which font to install and how to do it? I need help with this.
Thank you!
That seems like a question that would be specific to the operating system in your AppVM. I would recommend taking a look at the corresponding documentation or forums.
The only part specific to Qubes OS would be how to ensure that changes persist after reboot (that is: which changes to make in the AppVM and which in its TemplateVM). If you have trouble with that, you could post your questions in this same thread 