A good tip when dealing with unknown formats: First read, import or copy from the place where you want to add information.
You then have the correct format and you paste or import it to another editable source like Excel. When you add something in Excel you can copy the existing rows and paste into free rows and then edit them.
When you then copy or export from Excel it will be, hopefully, in the correct format.
I always do the same when programming things like radios, always first read the correct format and edit, and do not try to create anything from scratch. Of course you can save the Excel file and reuse later without having to first copy or import from the source.
I just verified by copying some rows from analog frequencies in a favorite list in Sentinel and pasted into Excel. Copied two rows in Excel and pasted at the end and edited some values. Then copied all the rows and pasted into Sentinel. But you have to mark only the Excel cells up to the last one that are used in Sentinel, not the whole row with empty cells. You also have to prepare Sentinel to first add lines so that the paste will match the exact number of lines you copied from Excel. If you only added 5 lines in Excel you can copy only those lines and paste into the marked lines in Sentinel. It looks more complicated in writing than it actually are doing it.
If you only add one cell like frequencies or name tags and paste into one free cell in Sentinel it will automaticly add the missing lines. As it doesn't do this when pasting a whole line, and responds with that you have to match the exact area, must be a bit of a failure for the software coder of the Sentinel program.
I also verifed copying from Sentinel to Notepad and edit there and then paste back into Sentinel. It works the exact same way as using Excel but you don't have to worry about including empty cells.
/Ubbe