Ha! Discovered a small note in one of the side windows, which gives this URL: http://claudia-dzengel.com/

Could be, but it'd just be a vague guess (i.e. I'm not comfortable putting this guess on the map). What I can say is that Wohnpartner isn't visible there anymore (hence my removal). The nearest Wohnpartner Lokal seems to be in Pappenheimgasse (https://www.wohnpartner-wien.at/ueber-uns/wo-sie-uns-antreffen/).
Regarding shop=vacant: the Wiki mentions that use of this tag is disputed... What's the use case for tagging this? Who would use this information how? (I find it helpful to have usage in mind when mapping.)

It's not quite clear to me what's going on there. There's some rather obscure art in the windows but no sign or opening hours I could discern. So I'm not sure if there's still a shop there or if it's been converted to something else, if it's being used or what it's being used for. Mysterious! ;-) What do you recommend in this case?