In 2018 and years prior, the USGA and R&A placed fairly tight controls on who could mark and lift a player’s ball on the putting green (and elsewhere on the course). The relevant portion of the 2018 rule reads as follows:

A ball to be lifted under the Rules may be lifted by the player, his partner or another person authorized by the player. In any such case, the player is responsible for any breach of the Rules.

This applied to the putting green as well as anywhere else on the course, and it required explicit approval for each instance. A player could not, for example, say “I authorize my caddie to lift my ball at any point today.” He had to give approval each time.

In 2019, the relevant portion of Rule 14.1b reads almost the same:

The player’s ball may be lifted under the Rules only by:

• The player, or
• Anyone the player authorizes, but such authorization must be given each time before the ball is lifted rather than given generally for the round.

However, there’s also an exception:

Exception – Caddie May Lift Player’s Ball on Putting Green Without Authorization: When the player’s ball is on the putting green, his or her caddie may lift the ball without the player’s authorization.

If a caddie has lifted a player’s ball, either the player or the caddie may replace the ball.

So, very little has changed here, except that on the putting green the player’s caddie has the authority to lift the player’s ball, should they choose. The rest of the Exception reads that “If the caddie lifts the ball without authorization when it is anywhere except on the putting green, the player gets one penalty stroke (see Rule 9.4).”