For multi-monitor setups allowing child windows to be separated from the single host app window would be extremely useful, as per Excel: https://blogs.office.com/en-us/2013/02/07/open-excel-workbooks-in-separate-windows-and-view-them-side-by-side/, or, ideally, using Visual Studio's tear off windows, out of the main app into some spare screen space.

Although you can stretch the app window across multiple monitors the break between two monitors never sits in the right place (ie the break between two child windows) and so you end up using a single monitor.

In Visio, it's common to have multiple ShapeSheet windows open at once, either displaying master and instance, or one for each sub-shape in a group. In my setup (28" 3840x2160 @ 125%) I recon on one drawing window + a maximum of five ShapeSheet windows as being usable, but beyond that you spend all your time scrolling and switching windows. One of the real benefits of a large screen in Visio is being able to see more ShapeSheet sections at once and this is limited by only being able to use a single monitor.

From the drawing window perspective, other scenarios might also include: a) master details view - for example a one window for a floor plan, displayed alongside other windows of the same page at different zoom levels and areas of focus, b) multi-page view - ie one window per page

Bottom line - I've got plenty of screen real-estate and I'd like Visio to make full use of it so that I can be more productive.

I am a solutions architecture consultant and have been using Microsoft Visio Premium 2010 since it first came out. In 2013, I recommended to a client of mine to install Microsoft Visio Premium. They installed 2013. I was mortified to find that the advanced support for UML and database modeling was missing. I told my client that they must have installed standard by accident. Because Microsoft would never lose backwards compatibility. I was wrong. They had installed Professional. The feature were discontinued without warning. A Microsoft product that is not backwards compatible. The master class list is critical to creating multi-diagram UML models. All of the metadata associated with a previous version of my UML file was destroyed simply by opening it with 2013. I found the change unconscionable.
I used the product to create new diagrams anyway, thinking that I would need to get used to it. However, I found that the product was riddled with bugs as well. I had created a large diagram with about 200 classes on it and many lines. One day when I opened the diagram in a manager’s meeting, my lines were all moved to seemingly random routes. When I grabbed the end of a line, a green dotted version of the line materialized where I had previously routed the line. When I let go, my line moved back to where I had put it originally. I had to do this with all of the lines on the diagram. This happened without anyone touching the model. The same problem happened over and over until I requested that my client uninstall Visio 2013 and install Visio 2010. I have looked at later releases but I will not upgrade or recommend that my clients install anything but Visio 2010.
I suggest that Microsoft repent of the mistake of violating backwards compatibility, and return the features that were removed by 2013. These features are important enough to keep me forever in 2010, or abandon Visio altogether for a more expensive modeling product. I would also like to hear the argument for removing these features. I would like to suggest to the management over this decision maker that they have some principles that guide such decisions so as to avoid this sort of backlash.
I have been a fan of Microsoft products since Windows 3.1 came out. But lately, I feel like Microsoft has failed to understand their place in the market. Stop trying to look like Apple. The reason the business world still uses Microsoft is because of backwards compatibility. Where do you think loyalty comes from? No one wants their software to change drastically especially when the change does not add significant functionality. Simply changing the look and feel is a recipe for sending otherwise loyal customers elsewhere. If you want to sell a new shiny, create something different. Stop messing with what people know and love.

Visio should natively support more than one text block per shape OR CONNECTOR.

Database ER connectors are a natural for this; I can imagine an overall "relationship" text block somewhere in the middle, with text blocks at either end as well. (A secondary issue with connectors is that some of the specialized built-in connectors don't accept modifications, such as line width, gracefully, so I end up using "regular" connectors).

In shapes with distinct areas (i.e. that have one or more lines crossing the shape) it makes sense to have a text "title" in the upper region and a "description" or "details" block at the bottom.

Flowchart "decision" blocks is another example. Either the shape should have text blocks at the vertices, or the connectors should support text at their endpoint (e.g. "yes", "no", ...).

In almost every diagram I create I struggle to work around the "one text block" paradigm.

#TextBlock #Connector