A good shortcut, but a one-trick-pony; you can only use it for one set of tags.
Here's my trick.
I prefix the tags with the subject; for example "Sched" for scheduling.
So my tags would be Sched-Today, Sched-Tomorrow, Sched-NextWeek, ...
To enter the scheduling tag, I start typing Sched
Instead of a list of 300+ random tags, I'm presented with a list of 4 scheduling tags
I can use the same trick for different sets of tags; Project, Vendor, Budget, ...