If you're trying to add a custom format in Excel and you see the message "No more custom formats can be added," it means that you've reached the limit for the number of custom formats that you can create in that workbook. Each workbook can contain a maximum of 256 custom formats.
There are a few ways to work around this limit:
If you still need more than 256 custom formats, there are a few third-party add-ins that can increase the limit. One option is Format Painter by AbleBits, which allows you to create up to 1,000 custom formats. Another option is Custom Number Formats by Office Labs, which allows you to create an unlimited number of custom formats.