There already is a tree view for N:N relations, but I think it would be great to be able to search for a record for a lookup field via a treeview. A common example would be

• selecting a product: the user would be default see the product families and is able to search these items or scroll through these and open the right family to drill down and select the right product.

Ideally the tree hierarchy could be based on 

• a self-referencing 1:N relationship such as products and product families
• a hierarchy based on another lookup/relationship from the "target" entity. 
  • Suppose  you have a lookup to select a country (custom entity)
  • Every country has a lookup (N:1) to another entity "Continent"
  • when opening the lookup search window, the user would see the lists of continents. The user is able to expand a continent which displays the countries linked to that continent and to select one. The selected country is completed in the lookup field.

• a third option would be able to use different levels, where the hierarchy is composed of different entities and different N:1 relationships (Continent - country - State) but might be too complex...

The idea would be create a better "multi-select" optionset.  The control could show all available values, and the user could pick which ones but just clicking the dots, the backend would make the N:N link.  Obviously would not work for large datasets.

One of the great features of the out-of-the-box Editable Grid is the 'Group By' functionality. 

It would be great to have the same functionality for read-only grids as well. Often it is not desirable to use Editable Grids, but the 'Group By' still having the Group By feature available would be great. 

Not sure if this has been done already but it would be really useful to have a drag and drop stream lane PCF that allows users to drag opps or cases from one stage to another.

The standard control for Rollup fields includes both the rollup field and the Last updated date field. In many scenarios the last updated field in irellevant and only confuses the user. So it would be nice to have a control that just shows the actual rollup field.

It's something alot of people have wanted for a while but the ability to directly copy a image from a screenshot on your computer and paste it into the body of the email content and have it display contextually. Obviously it need to auto-attach the screenshot as an attachment first before displaying it contextually.

I imagine this would only work for 1:N relationships with a whole number column on which the selected View is sorted on. The grid would allow either drag and drop re-ordering (or at least up/down arrows on each row) that re-orders the records via updating the whole number field.

In my case we are building out some data (legal Clauses) to insert into documents and the order of insertion matters. I'd build it myself but at this time at least the Project doesn't have budget for me to learn how to build a custom control and build/test it.

A control to create dynamic FetchXML queries and show results in a supported way. Aditionally could save que query as SQL as savedqueries or userqueries.

If audit logging is turned on for a Dataverse table you can view which fields were changed and what they were changed to or from. This can be added as a standard tab in a Model driven app. This can't be added in a canvas app, just showing the rows from the Audit table gives includes AttributeMask field that is a comma separated list of column number and data, which even the docs say not to use.

MS Docs: Retrieve the history of audited data changes - Power Apps | Microsoft Learn

ability to show/hide password fields with an 'eye' icon. Passwords must not be visible in HTML source code.