Hi,
You can easily add/edit text notes. In MindMup 2 we split the attachment feature from MindMup 1 into two: attachments (files on drive) and text notes (simple text, editable in the map).
The old rich text attachments caused too many problems, as people would just paste invalid HTML and break everything, then complain that MindMup is broken. Plus we would never be able to offer full rich text editing support that google writer already provides, so there wasn't much point competing with that. So for users that need just simple textual comments (such as the one in your example), it's best to use notes feature:
https://www.mindmup.com/tutorials/notes.html -- this allows you to also easily export notes into a writer doc or an outline. Users that need full rich text support are better off just creating a google writer document and attaching it to the map.
The attachments that you have are read-only so there's no data loss, but i'd suggest copying and pasting the contents into text notes. We don't plan to add rich text editing for attachments back, but we will add some rich text markup capabilities for notes later this year (such as basic formatting, bullets, italics, bolds and hyperlinks).
I don't understand what you meant by "If not could you send the file extension for Chorome "MindMup Desktop - Free Mind Mapping", in order to keep lectures." - can you please let me know what you need me to send?
gojko