Tracking unspecified custom markers

The error message I got when I included FRT in the project list was somewhat opaque. But I did figure it out: I had a custom field marker in the FRT that PTXprint didn't know what to do with. I have these all defined in the "custom.sty" file for Paratext. But in custom.sty file I also have all kinds of other specifications too, which I don't want coming into PTXprint! So, I am hoping to just use the Style sheet in PTXprint to do all the tweaking I need to do. This way I'm not having to chase my tail all around to figure out where a layout or style problem lies.

So, let's assume a normal MTT user will NOT use the custom.sty option (since they won't know how to edit it anyway). If there are any custom markers in the project (made by a consultant, for example), these would likely be in the custom.sty file. In this case, the project would PASS the Basic Checks in Paratext. But if the custom.sty is not used in PTXprint, then the message about running the Basic Checks to fix the problems won't help the MTT.

So is it reasonable to have PTXprint do a run through the entire project and compile a list of field markers and make note of any which it doesn't know about? These unknown markers could be reported to the user for them to fix them (say there actually is bad data (typo), and the Basic Checks would help with those), or offer to add the valid custom fields to the PTXprint Style Sheet. Then at least PTXprint would know about all the fields in the project.

Currently, I don't know of any way to see all the markers in the PTXprint project files, to know which are missing or unspecified in the stylesheets available to PTXprint at the time I want to print something. Is their such a feature that I'm not seeing? Maybe at the bottom of the Style sheet?? I do recall there is some residue at the bottom of the list. But it doesn't seem to dump unknown markers there.

Start by reproducing the FRT case with custom markers defined in custom.sty but not in the PTXprint Style sheet. Review the existing Style sheet and Basic Checks behavior, then define how a full-project marker scan should report unknown fields or offer valid custom fields. Done means the resulting behavior clearly distinguishes typos from legitimate custom markers.