Just a comment and a couple corrections. The USGA never uses LCP for any of its national championships. I volunteered at the Womens Open in Birmingham a couple years ago and it rained all week until the event. The players were at Topgolf to practice because the course was closed. Water was evident throughout the event in fairways and elsewhere. Mud balls were the order of the week. Any other tournament would have invoked LCP, but the USGA refuses. Same thing in Florida where I am a rules guy for the FSGA. When we hold USGA qualifiers for Open, Amateur, and others, never can use LCP.
As for corrections, it is not true that one must always mark a ball to be lifted. In fact, the player must mark only if the ball is to be replaced. Exception is the LCP rule. For some unknown reason, the ball must be marked before lifting, even though it may be placed as much as a club length away. Any other situation, such as when taking relief from immovable instructions, the ball does not have to be marked.
When using LCP, it is rare and not recommended to permit it throughout the golf course for the reasons mentioned about obtaining relief from unpleasant situations. Usually it is reserved for “closely-mown areas” only. As for moving it from fringe to green, this is not permitted. The ball must remain in the same area of the course in which it lies, the general area. The putting green of the hole being played is not part of the general area.