I believe that customized service types for Custom x are on the wish list. What's the point of having "Custom 3" when you do not remember what it stood for? All texts for service types are fixed in memory but it would be possible to have Sentinel write new ones for Custom x in a free memory space and the firmware to look there first to see if there where texts stored there that would replace the default Custom x.
It's just a number reference for each TG and conventional frequencies being programmed and the scanner then filters using the number and displays the service type name by fetching the text from another memory area. Altering that text will change the displayed text for all TG's and frequencies using that service type number. It's not a big change, the Custom types are the highest numbers of service types and are easily filtered out in firmware code. Any normal coder would do the change in less than one hour but then the Sentinel program needs to be changed and then there's the quality department that needs to scrutinize the code and do test to see that all operations are still intact. That's what takes most of the time and will cost money. UPman did a lot of that kind work in his spare time and used beta testers that didn't ask for money, just to reduce costs that management couldn't say no to and gave scanner users a lot of new features.
/Ubbe