You might have guessed I'd end up posting something, lol.
Seems you've got the info you wanted, but there's always more than one way to etc....
If you do the 'inspect' thing as suggested on any WGT page, click the 'console' tab, then type in...
userID
...and hit enter, you'll get your own ID number, (unless you aren't logged in, in which case you won't).
If you go to a members profile page, do 'inspect', and type into the console...
profileUserID
...then hit enter, you'll get that members ID number.
If you want the digits grouped to make the number easier to read, then type one of these into the console instead...
parseInt(userID).toLocaleString()
or
parseInt(profileUserID).toLocaleString()
Make sure you use the correct capitalization as shown, when typing into the console, although you may get intellisense assistance as you type, and therefore options to pick from.