Following up this, on adding a measurement toolbar (or annotation toolbar): This is a functionality most DICOM viewers have. They even have text, arrow, ellipse, circle, pen options - but instead of markups, these are annotations (kinda like Zoom or video call annotations on the screen). With the exception of ruler and angles, they don’t return any measurements. I think a user with a medical background would expect to see this in Slicer. It is a very common thing for doctors to want to measure something to just see the number. “Let’s see how wide the eyes are, hmm, 2.4 cm is wide for this age…” kind of situation.
See the web-based viewer our hospital uses:
Previous mouse mode button with all markups nodes available under the expandable menu provided this functionality for users who didn’t care about the line markups node as much as being able to see the distance. With the current Markups toolbar, it is still possible, and as a heavy user of fiducials, it is still very straightforward and easy for me. But I understand the complexity this toolbar might present for a new user. If the idea is to simplify the use of Markups for some users, I like the option of adding a measurements toolbar - which uses the functionality of Markups and still creates lines, ROIs etc. in the scene but hides all the extra functions.