In a microflow you should grab the location of the current user and add it to the list with all your other markers before you show the page.
Hope this helps, otherwise be more specific on what part is not working.
If I understand correctly is that when you have a current location of the user you want to show that and if not show all the markers? If so, check if the current user has a location and show that otherwise retrieve all the marker locations and pas that to the page.
Use the on change action of this widget to trigger your microflow where you can do the stuff I described above.