I have searched Google maps and found none, but I saw that in my city many bus stops are not marked, so I hoped you could help me. Less than 300m from public transportation would be great.
I am disabled and moving to Vienna.
You can search for stores on the Starbucks site, here are the results for Vienna, Austria. There are many stores and many are near U-Bahn stations and/or tram and bus stops.
and a close up showing the tram stop:
But there are plenty others that may be more convenient for you.
AND, although I'm a Starbucks fan myself, I'll point out that Vienna has plenty of other coffee shops that and excellent public transport. So you'll be able to find plenty of choices ...
I notice in the comments that you're looking for somewhere to sit and work.
Apparently, Vienna has a very high concentration of co-working spaces purpose-designed for the sort of thing you're looking to do. From this article:
It lists 12 coworking space initiatives (so at least one is likely to be accessible), three of which are part of a network called Konnex which also offers members:
Some of these services might be useful to a disabled newcomer to a city, and initiatives like co-working spaces of like-minded pro-community people like this are likely to be a better way to make useful contacts and friends in a new city than Starbucks.
In my experience, the kind of people who join and run initiatives like this will be very enthusiastic about helping a newcomer with specific needs to settle and be productive in their city.