You can override the ImageBrowser's _dblClick internal method to obtain the ID of the folder, which will be opened, and pass it back to the server in the read request.
The following script should be executed before the ImageBrowser popup is opened. This can be before or after the Editor is created.
oldDblClick = kendo.ui.ImageBrowser.prototype._dblClick;
li = $(e.currentTarget);
// "folder" is a Kendo UI Model instance
// obtain your custom folder ID from the model and assign it to a variable to be used in the function associated with transport.read.data
I suppose you are already sending your custom folder IDs via the read requests, so they are available on the client.
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