If you’re in Mesen’s debugger and choose Code>PRG Address Display>Inline Compact Display, then that will show the addresses on the left side of the debugger window as:
and that just means the ROM Address is supposed to be 3CE01 for that line.
It’s always like that… just truncate the left most hex digit from the CPU address and then replace that empty space with the information inside the [ ].
Also, if you open up your ROM’s .cdl file in a hex editor, then you can visually see the entire byte for byte Mesen Debugger formatting. All of the PRG Addresses, calculated above in this post, are the addresses to be used for your .cdl file.
(i.e. don’t search for CPU address CE01, when you should search for ROM address 3CE01. I’ve made that mistake MANY times… so it is possible to mess up your .cdl file in that manner, if you edit the wrong .cdl byte.)
The set 7th bit instructs MESEN debugger that a function/procedure starts at that byte.
The set 0th bit instructs MESEN debugger that that code has been run before.
The set 1st bit instructs MESEN that that byte is part of a data section. Data sections are represented visually different in the debugger.
EDIT: fixed many incorrect statements and added more info
FINAL-EDIT: .cdl files can be found in your Mesen\Debugger folder. And, to see changes from .cdl file edits, it is necessary to, in Mesen’s debugger, access Tools>”Code/Data Logger”>”Load CDL file…”, IF: File>Workspace>”Auto-Load CDL files” ISN’T checked.
Though, I’m unsure if MESEN only Auto-Loads a .cdl file when a ROM/game is loaded.