MarkItUp access to asset folder in Perch 3

I have to come back on customizing the markitup editor after upgrading from Perch 2 to 3. My latest thread on this can be found here: https://forum.grabaperch.com/forum/10-05-2017-customize-markitup-in-perch-3 I just realized that the access to the asset-folder is no longer available. I cannot upload an image neither attach a file. When clicking the icon nothing happens. I am on Perch 3.0.10. Maybe the reason is because Perch 3 handels the asset-upload slightly different? Here is my config-file.

Perch.UserConfig.markitup = function(){

var get = function(profile, config, field) {

return {
nameSpace: 'markdown',
previewParserPath: '',
onTab: {keepDefault:false, openWith:' '},
onShiftEnter: {keepDefault:false, openWith:'\n\n'},
markupSet: [
{name:'Bold', className:'fa fa-bold', key:'B', openWith:'**', closeWith:'**'},
{name:'Italic', className:'fa fa-italic', key:'I', openWith:'_', closeWith:'_'},
{name:'File', className:'file-upload fa fa-file-o', openWith:function(markItUp){miu.ImageUpload.upload(markItUp,'markdown',true);}},
{name:'Link', className:'fa fa-link', key:'L', openWith:'[', closeWith:']([![URL:!:https://]!] "[![Title]!]")', placeHolder:'Your text to link here...' }
]
};
};

var load = function(cb) {
cb();
};

return {
'get': get,
'load': load
}

}();

Thanks a lot for helping me!