Hello Carlos,
Thank you for the feedback!

1. Favicons:
The addon should automatically download missing favicons, there is several events that should trigger that, though if it's interrupted (for example by restarting browser), it won't start again, unless something triggers it again.
Now that I think about it, maybe I could improve this by actually recording a "successful finish" so that I'm sure the favicons were fully processed.
I'm just thinking out loud here.

Anyway - there is a secret button "Download missing favicons" in the secret Debug options section:
https://github.com/fastaddons/GroupSpeedDial/wiki/Debug-options

2. import - sadly yes, importing any data while having "Replace existing dials" checkbox checked, will replace all data and settings.
Note that you can always revert recent changes from the main menu / "Undo last change" (or in "History / backups").

3. the batch operations are very hard to implement :(, but there are some global Dials settings in the Options page / Dials tab.
If you are missing some options here, please let me know which and I can try to add them.

4. batch groups edit is actually planned for the near future.
I will write a post about it when the new version is released.
And I'll also try to make a video about it.

For further feedback, please write me email: admin@fastaddons.com
I'm reading all emails and then adjusting my todo list based on the feedback I receive.

Best regards,
Juraj Mäsiar