If you export your bookmark from Diigo, make sure you use the Delicious export, not the Netscape export. (Their Netscape export is broken, and they don't seem to be interested in fixing it.)
To correctly import the tags from a [SemanticScuttle](http://semanticscuttle.sourceforge.net/) HTML export, edit the HTML file before importing and replace all occurences of `tags=` (lowercase) to `TAGS=` (uppercase).
Shaarli cannot import data directly from [Scuttle](https://github.com/scronide/scuttle). However, you can use this third party tool: https://github.com/q2apro/scuttle-to-shaarli to export the Scuttle database to the Netscape HTML format compatible with the Shaarli importer.
* For compatibility reasons, check `Prepend note permalinks with this Shaarli instance's URL (useful to import bookmarks in a web browser)`
* In Firefox, open the bookmark manager (not the sidebar! `Bookmarks menu > Show all bookmarks` or `Ctrl+Shift+B`)
* Select `Import and Backup > Import bookmarks in HTML format`
Your bookmarks will be imported in Firefox, ready to use, with tags and descriptions retained. "Self" (notes) shaares will still point to the Shaarli instance you exported them from, but the note text can be viewed directly in the bookmark properties inside your browser. Depending on the number of bookmarks, the import can take some time.
You may be interested in these Firefox addons to manage links imported from Shaarli