A while ago there was an action that was slowing down the typing when a certain token was being used (don't remember if it was the %FinderSelection% token as well, and if it was this same Get Attribute action)
but I tried with the Set Attribute action and I get the same thing. Trying to type something gets super slow, for example if I want to change the variable's name. The only way to work around this is to remove the last % (so %FinderSelection) and when I'm done typing, adding it back again.
@peternlewis are you aware of this?
I have KM Version 11.0.2