Hello and thanks Phyllis and Igor, I find the Cinelerra subtitle editor very good, even much better than many applications dedicated to the exclusive creation of subtitles. Only I miss being able to see these in the preview, but hey, you can work perfectly with them and I do not think it is necessary to see them either.
To convert .udvd to .srt or .ass is as simple as:
ffmpeg -i subtitle.udvd subtitle.srt
or
ffmpeg -i subtitle.udvd subtitle.ass
without any problem.
my favorite is .ass because you can easily customize how they will look.
What I think needs to be improved is the wizard to load or save to navigate to where the file is to load or save... it is a bit tedious to have to enter the path by hand. I know this is a copy and paste of the address, but this for a beginning person is a difficulty.
Thank you both very much for the interest.