Since it does not look like Mendix Marketplace/App Store has any widget for this, it may be necessary for you / someone else to create such widget that can allow storing images on paste from your clipboard.
Here are some links to get started with writing code that can get the image from your clipboard when pasting:
These are for images, but files/documents should also be possible to obtain :-)
To store file data to a FileDocument (or a sub-entity of it): https://apidocs.rnd.mendix.com/8/client/mx.data.html#.saveDocument
Additionally, you can find documentation to get started with writing Mendix widgets here:
There’s also pluggable web/native widgets now, but it is not something I have worked with.
I hope this helps you,