Freeze while finding/replacing large amount text

I attempted to replace tabs with spaces in a ~6000-line tab-indented file. Code's UI locked up pretty much immediately, and a single CPU core was pegged for a couple of minutes. After a few minutes, Code had performed the replacement properly, but it had rendered the whole app unusable in the meantime.

For kicks and to reproduce, it was this file: https://github.com/elementary/wingpanel-indicator-network/blob/ce10f927cc7adb4843aafa536b12968bd512883b/vapi/libnm.vapi

Reproduce the freeze by replacing tabs with spaces in the linked wingpanel-indicator-network/vapi/libnm.vapi file using Code's find/replace. Profile the operation while checking UI responsiveness; done means the replacement completes without rendering the application unusable.

Written by the indexing model from the issue text.