Hi Gianluca Ghioni,

Check the attached OML. Hope that helps you. But in this case, you cannot use the Select All option. 
Check the SetInfoAboutSelectedItems Screen action in the "MultiSelect_ReactAndMob" block.
I have added one input to get the max number to select.

Regards,
Mounika

Hi Gianluca,

I have been meaning to develop this feature for a while.
I'll see what I can do, then post back here at the end of next weekend.

Kind Regards,
Chris

Hi Gianluca,

Thanks for your patience.

I'm excited to announce MultiSelect_ReactAndMob version 1.9.1 has been released.

Bugs Fixed

• Fixed a CSS Bug where the "Select All" and "Select All Results" labels were right aligned, when placed into a ancestor CSS context, whom contained "text-align: right".
• Fixed a bug: the number of items to be (de)selected (part of the "Select All" and "Select All Results" checkbox labels), did not account for disabled list items - which cannot be selected.
• Fixed a CSS bug where icons added into the dropdown bar Placeholder were being displayed using block layout, rather than inline.

Features Added

• Added new placeholder: allowing extra flexibility in the "Select All" and "Select All Results" labels
• Added option: Limit the number of selected items

Hope this helps!

Please let me know if you have any issues!

Cheers,
Chris.