I've prepared a workaround for you; it assumes that all files that you want to multi-select are in the same folder. My current method works only if you want to select TXT/DOC files, but you can easily adjust the filter. Just run the green method. It works in 2 steps:
1. Select the target folder, by selecting any file in the target folder with the file-dialog.
2. This will fill a table with a list of all files in that directory (you could also add a filter there, if required), where you can then set a boolean-column to indicate which files you want to select. The table is basically the result of your multiple-choice-selection.
Hope this helps
Thank you Alex, the idear is good and i can create a solution for me.
But your Model makes not what you want. you are using a wrong path for import...