deleting text in command mode replaces the contents of the clipboard

[russ-te2]

Often I want to paste a line of text from another source into an existing line, when deleting the
relevant parts of the target line this clobbers the previous contents of the clipboard, rendering
command+v useless. Is there a way to disable this behaviour?

[keevan]

This is quite normal/default vim behaviour. You might find visually selecting what you want to delete v + movement, then pasting p an alternative to your problem.

That said, there is an option for you to accomplish what you originally wanted, just from configuration, using something called the blackhole register. For example, if you want all delete commands to never populate the clipboard (and instead be sucked into a black hole), you'd add delete* as the configuration value

Example: