For God's sakes I've spent 20 minutes on your site trying to figure out how to download your demos. Every link takes me that USELESS TelererkUIForBlazorSetup.exe. Syncfusion my be the worst but at least you don't have to google something that should be so redundant it's everywhere.
I finally gave up and had to google it to find it on Github. Absolutely worst experience ever.
Telerik Multi Select to have optional top level header item with check box & title "Select All" [Localizable].
If all items are selected, the display box of the Multi-Select should show "All Selected" instead of list of selected items.