Streamtuner2 allows to bookmark favourite streams/stations.
Use right click for a stations context menu ▸ bookmark
Or just press F8 on a selected radio.
Else use the main menu Station ▸ bookmark
Once bookmarked the station is listed under bookmarks ▸ favourite.
Additionally every appearance of the station in other channel tabs gets a ★ star icon.
Entries can be removed from the bookmark list again. Use Edit ▸ Delete or the DEL key for that.
You can also manually adapt an entry via Station ▸ Edit or by pressing F3.
The bookmarks tab can display other categories besides "favourite". For example the search feature creates a "search", while the "timer" and "links" plugins also display lists here.
There's ato provide for favourite subcategories. You'd usually move items there per . It's somewhat of a workaround, however.