Hi Krishna,
In the boostrap multiselect widget select datasource as microflow and inside microflow you can check your condition and based on which you can return needed list , regarding selecting via mouse i am not sure what you mean because for seleting any record we have to have clicks.
You can also try this autocomplete multiselect , but it requires bit more configuration as it stores response in json and you have to create json structure and use 'import from mapping' to get the selected value
Hope it helps!