Hey @Vanchencio I just stumbled on how to copy your Speed Dial contents over. I could not find the file/folder name that contained the Speed Dial data in my Opera Stable profile. The Speed Dial contents do come over via Sync, but they don't populate in the "main" Speed Dial of Opera GX. Here's what I did.
So first, I synced my Opera GX browser using my Opera account.
Then, I went to Bookmarks (either in the Opera menu or Ctrl+Shift+B). Look for "Other Speed Dials".
Right-click in an empty space and click "Select All" (assuming you want all of your Speed Dial websites, otherwise, you can individually click the ones you want).
Right-click on one of the Speed Dial preview icons (I don't know what they are called) so you get the "Copy" command in the context menu.
Finally, click on the Speed Dial folder in the bookmarks menu on the left side, then right click in the empty space and click "Paste".
Boom. You're done. Hope that helps a little! - Reyk