The current Viking zoom level (in 'pixelfact') is shown all the time in the status-bar.

Perhaps show both Google and OSM etc. zoom levels, (or maybe they are the same), along with the pixelfact ones (that are real hard to do a Google search about.)

Yes, the manual says

2.8 Zoom Level
Viking uses a zoom level measured as a pixel factor in Metres Per Pixel (MPP), hence this may also be referred to as a zoom factor. By default in this document the zoom level refers to Viking’s MPP definition unless otherwise stated.
This is in contrast to Tiled Web Map systems such as OpenStreetMap which use the Zoom Level as a measure of how much of the world is visible on the map.

That's all well and good. But nonetheless, it's time to show zoom levels other people use too.

Also, right on the man page we see

[-z | --zoom ZoomLevelOSM]

therefore it at least deserves a place on the screen when showing zoom levels.
I don't see any other (pixelfact) viking zoom options there on the man page.

But then again in
Layers > New Map Layer > Zoom Levels
there are only pixelfact zoom levels and no OSM zoom levels, hmmm.

I might be wrong but apparently we are dealing with a
https://en.wikipedia.org/wiki/Shoe_size
problem, and both systems should be shown in all places.
(Or at least show the one that I've heard of :-) )

I think the simple way is to address the original problem is a dynamic tooltip (instead of the static one) on the Zoom status-bar value.
Then also see if similar tooltips can be added elsewhere.