Some kind of animation for the splitters when you collapse/expand them?
Even nowadays there are people not used to the web environment, and if the collapsible pane just hides instantly (or almost) they will first think 'Where did my *whatever* went!?' so having some kind of easing they would see where did it go.

Adding animation on splitter would be better, currently there is no animation on splitter. animation like slide,fade in, fadeout would be fine.

Allow sliding panels much like you do for the AJAX splitter control.  This feature would be very nice if it was working with tablets.

Expose the ability to set the content of a pane in a stable state. And not shrink or expand when the splitter is adjusted. The content should overlay each other as demonstrated in the video.

Hi Team,

I would like to request a way for the Kendo UI Splitter to be resize automatically if it is within a hidden container instead of having to call resize.

Thank you!

See Kendo UI v2019.1.220 Distributed Source Code module kendo.splitter.js _resize() method (Lines 285-240) 

1) The splitter _resize method iuses jQuery width() and height() methods to set pane sizes.

2) These methods get/set the clientHeight and clientWidth of the pane element rather than the offsetWidth and offsetHeight. 

3) If any pane has a border or padding, the last pane will extend beyond the limits of the splitter element.

4) Recommend using offsetWidth and offsetHeight to get/set all pane sizes. 

Currently, when the size method is used, the pane parameter could be set using string or jQuery element. I would like to have the support of setting the pane using integers. For example, setting the size of the first pane could be as follows:

var size = splitter.size(1, "40%");