Hi Partner,
We could use Jquery in Entity List to control the filter style.
For example, I have a filter panel in my support case list page, and I found that its style is controlled by ".entitylist-filter-option-text" class.

So we just need to update its style "width" when loading this page.
I add the following code into entity list and have a try.

$(function () {
var timesRun = 0;
var interval = setInterval(function () {
var panel=$(".event-info");
if (panel.length!=0) {
clearInterval(interval);
for(var i=0;i
It worked well! the panel has updated to 500px.

So you could change the filter panel to whatever length you need.
Best Regards,
Leo