Tag recommendations would occur once one adds a #tag on a line, you are then prompted (like the link suggestion box) with commonly associated tags to the one you just placed (also rank tags that are associated with other links in this note, or notes that are a degree or two away).
A highlight/cursor will be on the next suggestion, shift+enter will allow you to quickly add them to the line. Also a box with a tag/word cloud allows you to see even more options & click to add them.
Every time you add a tag (by typing or selecting) another # is begun for quickly adding/typing an additional.
With this you could type one tag and in a matter of seconds have 10 related tags on the line.
Perhaps this is also available in a panel, similar to Backlink panel, view tags that are in the note that are linked to/in this note, tags that are commonly associated with the tags currently in this note, etc.