I would like to see away to cross reference releases to the API docs.  So when a new method, property, etc. becomes available for a control or framework, I can see what release it was associated with.  This will permit me to upgrade apps to specific versions. Or during an update, I can see where a breaking change occurred.  I'm sure lots of other benefits could come from that.

The Detailed description In:
https://github.com/telerik/kendo-ui-core/issues/3903


Bug report
Currently, DataSource bound Spreadsheet throws "Unsupported for multiple ranges" error when attempting to delete the content from multiple not adjusted cells.

The error is thrown by the values() method:

values: function (values) {
    if (this._ref instanceof UnionRef) {
        throw new Error('Unsupported for multiple ranges.');
    }
    if (this._ref === kendo.spreadsheet.NULLREF) {
....
Reproduction of the problem
Go to the DataSource Binding demo;
Select a few cells using the Ctrl + click;
Press Delete button on the keyboard;
"Unsupported for multiple ranges" error will be thrown from the values() method;

This bug has not been resolved in Version 2018.3.911. 

I could attach a screen shot of this, but there doesn't seem to be a way to attach anything.

It would be nice to know what version a function or method was released in. Please add the version to the documentation so users can easily understand if the function is available in the version they are using.

There is s set precedence among many of your Kendo UI controls in providing a tool tip option, yet the NumericTextBox is not one of them. 

Radio buttons fire events and web developers rely on these events to capture data or initiate a process. I fail to understand why something so basic to a control is overlooked, yet you provide this functionality to most of your other controls. 

it's looks nice if we have an option to move chatbot image to either on first or last of message for multiple messages (currently the chatbot image located on the last message)

In some specific cases, it is required to show a bubble within a bubble in the Bubble chart. This is required to demonstrate some specific property within the bubble.
e.g.
The bubble position shows which project.
The bubble size demonstrates projects size with respect to the program.
The bubble within the bubble shows the current progress of the project.

When using a grid against a large table with server side filtering (ToDataSourceResult)

ToDataSourceResult builds a SQL query that converts the search string to UPPER() and therefore prevents the database from using its indexes. As SQL comparison is case insensitive that LOWER() is unnecessary.  

As we have may grids where this is an issue it would be time consuming to build out manual filters for each grid instead of using ToDataSourceResult

This was discussed here and there was no solution at the time:

https://www.telerik.com/forums/grid-filtering-on-text-using-lower-in-sql

I would liek to request an option to tell ToDataSourceResult() not to use LOWER() in the sql?

See ticket #1339310

Displaying multiple columns on vertical resources on kendoscheuler resources.

Currently, when all are enabled, it's impossible to scroll, because either multiselect starts or drag&drop. Tested on iPad OS X 11.4

Any widget with the Template property should have a TemplateUrl property which allows the markup to be placed into an external html file similar to TemplateUrls in AngularJS components.

kendo MediaPlayer should allow set playback rate, allow user increase/decrease playback rate.

Like the event parameter of series.markers.visual contains the according dataitem the event parameter of series.labels.visual should do so aswell.

Currently the media player only supports YouTube and local media files. In think it would benefit from supporting other media providers such as Vimeo and Metacafe.

Please support API access for private NuGet feed. It is more friendly to build servers and avoids user information leaking.
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ADMIN EDIT
Update from 1 Mar 2021 - At the moment we are looking at providing certificate-based access - a relatively new feature that seems to be the current best practice (issue, PR). While it does require a little bit of setup, it does not expose secrets in the URL, and does not require user credentials.
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Could be added to the combobox the pagination funtionality like Sencha Extjs library

I would like the additional barcode added.

https://en.wikipedia.org/wiki/Data_Matrix

A Data Matrix is a two-dimensional barcode consisting of black and white "cells" or modules arranged in either a square or rectangular pattern, also known as a matrix.