You never use it?
What about quickly constructing an array from pasted data? Cleaning up styling around hashes/dicts? Quick vertical alignment? Renaming vars/methods? Converting between single/double quotes or back ticks? Quickly constructing similar-but-different lines from a set of vars?
I use it more than any other editor feature except autocomplete.
Mandrake74144dMulti cursor is an amazing invention.
Here's what I do in the situations you mentioned:
I rarely paste data, and when I do, I transform it in an empty buffer using find&replace.
I don't understand what it could be used for in hashes
For vertical alignment there's select[+shift]+tab
For renaming a symbol the only failsafe method is the IDE's own. find&replace will give false positives, manually selecting will miss some.
Converting between delimiters is also a job for find&replace, or preferably a linter so I don't accidentally overwrite within literals.
And I don't have the kind of foresight to realise that the next line would be similar. Rather, I just copy and modify, which is somewhat slower but works afterwards.