"Select all" for multiselect combobox

[OlliTietavainenVaadin]

Describe your motivation

Sometimes you want to select all of the items available (or all except one, etc.). If there's more than a handful, clicking on them all is a lot of work. There should be an easier way to do that.

Describe the solution you'd like

It could be something as simple as a "select all" item in the dropdown

Describe alternatives you've considered

Maybe a "select all" button in the input?

Additional context

Lazy loading needs to be taken into account.

[jouni]

I feel like this could left as a responsibility of the application, to provide a button next to the combo box for selecting all.

But perhaps an extra item in the overlay would be a nice enhancement. Need to think about how to combine it with #4185

[mvysny]

If the button is placed to the left of the MSCB, the user will not see the list of all options and therefore can't really tell which items will be selected. On the other hand, placing the button into the dropdown overlay, above the items, the user will see the items and will see the checkboxes applied as all the items are being checked. I think the latter is a better UX.

[Levaimate]

Is there any news or progress for this issue? This is a function we would also like in our application without resorting to some hacky workarounds or an external button.