Hi!
I experience issue with Kate 5.0.0 (KF 5.7.0)
If I open minified file and select all (file contain ~150000 symbols) - Kate load CPU on 50% (usually from 40 till 50) and hang/freeze.
Issue since before moving on KF5. At this time not minified code with the same number of symbols are select with no problem.

Created bug https://bugs.kde.org/show_bug.cgi?id=345775