actually we have some zoom presents such as 100%, 200%, 400% and 800%
this are useful with MRI and CT images that have a small matrix but with conventional radiology (either CR or DR) the image is larger and those 100%, 200%, 400% and 800% zoom preset are too large and produce exagerated enlargment in most cases

I think it would be useful to have a "small step" presets

incremental zoom in order to have gradual slight enlargement and shrinking of the image.

I mean, a +10% and -10% hotkey (ideally assigned to the "+" and "-" keys) to allow the user to progressively enlarge or shrink the image to the desired zoom level by means of multiple keystrokes

Did you try CTRL + PLUS and CTRL + MINUS shortcuts?
There's also this one: hold CTRL and use MOUSE WHEEL.

great!!! I didn't know that it was already possible!!!

I think you should put those Ctrl+PLUS and Ctrl+MINUS shortcuts for +10 and -10% zoom presets in the "zoom image" dropdown menu otherwise user will never know that such a feature exists.

Another good idea :-)

just a reminder for this easy hack

Thanks :-)

fixed in 3.1.4 beta