Can I add a file (rather than an image) to attachments panel? How to manage such files later?
You surely can. Click on Attachments.
Press on plus button to add the file. You can add several files at a time. The file can then be renamed or deleted. To do that, right-click on the file and select the option you need.
I do not see the file I imported in the note (PDF or RAR for example). How do I find it?
Open the window with attachments.