Should I adress myself as a doctor (Ph.D.) when I am only waiting for the diploma to be signed? I have publicly defended my doctoral thesis over a year ago now, and it is published online. I have also finished all the other doctoral studies that are required for a Ph.D. in my field (I have an official e-mail regarding this from the Head of study affairs of my faculty). All that remains for the final and official Ph.D. status are the official papers signed by my university. This is due to the fact that I have continued extracurricular studies (some minor subjects, methodological studies etc.) at my university under my postgraduate student status and thus have not requested the official papers yet since it would end my possibilities for further studies. I have also applied for postdoc grants, but for the time being without results.

Against this background, would any of you recommend addressing myself as a doctor (Ph.D.) until I receive the official certificate from my university? For example, I have been part of multiple academic peer-reviewing endeavors within the past year, and the journal editors always refer to me as a Dr. in their correspondences. So I have just followed their lead.

I've searched and read different forums around the topic i.e., "when it is proper to be called a doctor?" There seem to be somewhat ambiguity within the responses given.
As I understand it, you have met the requirements for graduation but you have not applied for graduation yet, so you have not graduated. The degree of Dr. has not been conferred to you by the university, so you should not use it. 

The importance of this varies by country: in some countries such as Germany, this is explicitly stated in the university regulations. In the US, many universities have three official degree conferral dates every year (at the end of each term, see for example https://web.iit.edu/registrar/academic-calendar), and you are not expected to use the title before the degree has been conferred.

Others may address you as they wish, but trying to use the title yourself might be seen by some as dishonest.