My guess is they are cautionaries due to the auxiliary A natural, which is implied. Where in your second example the auxiliary has changed so only one cautionary is needed.
I’m guessing it’s because the default for a trill is up a whole step or the next note up in the key signature where possible. With three untied notes, the first would be what you input, but without input on the following two, Dorico uses the default. If you want the tie without the additional cautionary symbols, you could probably turn those off in the bottom panel.
I do agree. But since Dorico produces them as trill continuation I cannot turn them off. I have no control over them even if I untie them and try to manipulate them one by one. I attached the example file in my original post. If anyone can come up with a way to get rid of the unnecessary cautionaries, I’ll be grateful.
I got the effect you’re looking for by hiding the individual accidentals in Engrave mode. Works just fine there. I could hide the last accidental in Write mode, but not the second. Since Engrave mode is your last step in the process, this should be your solution until there’s a good way to hide individual cautionary accidentals under a tie in Write mode.