I typically make a copy of the file so that I keep the original one I submitted for e-file locked. Then in the copy, I delete out the 2025 estimate payment not made so that all the carryovers will be correct.

For client file numbers, I use 4-digit numbers. So I have four more characters available. So if this was client 2635, the copied file is 2635CORR (for correction) so it's super obvious which version to proforma. I also use "AMEN" for an amended return, "EST#" (EST1, EST2, EST3) when I'm just tweaking the next year estimates mid-year so that the actual revised amounts I gave the client will proforma.

Also highly recommend getting MyFTB TIA access for your CA clients so you can verify estimates yourself. Yes, it takes more time upfront, but way less on the backend when clients give you wrong info.