Sudden lag spikes when editing .xml layout files

In case anyone else encounters this in the future, I've found that if you click on the little man with the hat at the bottom right, enable "Power Saving Mode" and switch down Highlighting level to "None", it reduces the XML editing lag in complex layouts.

Once you make the edit, you can disable Power Saving and slide highlighting back up to see the changes in Preview.

Not ideal, but it prevents the constant pauses between keypresses whilst editing.

Probably the "Preview" tab is open? If so, just close it. The rendering process takes up a lot of processing power.