CAWless Mod is a modification that "cannibalizes" CAW Slots in order to add up to an additional 100 Wrestler Slots for menu-accessible mods to the game. The CAWless Mod has first been introduced as part of PacPlus included in WrestlePLUS for WWE 2k19.
For a long time, WrestlePLUS' PacPlus was the only tool that can enable the CAWless Mod as it required the change of the memory structure of the game which file-based tools like PerfectPlextra can't accomplish. WrestlePlus/PacPlus had to be running at all times while you play the game in order for CAWless Mod slots to work - don't shut it off before exiting the game or your save game may get corrupted!
In February 2022, BlindedByTheGrace managed to create a version of the CAWless Mod (titled "Additional Charater Slots in WWE 2k19") that edits the profile_dat.pac file (and thus works without having to run a program like PacPlus ) and released it as a beta where you can sacrifice the last 70 CAW slots in order to gain mode slots for Wrestlers/Mods.
Using the CAWless Mod means you sacrifice and thus lose your CAW/CAS Slots in order to have more slots available for mods (note that this mod is experimental, can lead to severe issues with the game, including loss of functionality that depends on CAWs as well as possible save game corruption that may be caused by this).
Additional Charater Slots in WWE 2k19 on the SmackTalks forum (Download and Discussion)