ubuntu 20.04 将dock栏合并到panel

The Dash to Panel Gnome Shell extension does exactly what you want and is highly configurable.
You can install it from Ubuntu software (search Dash to panel), or using  the terminal with the command

sudo apt install gnome-shell-extension-dash-to-panel.

Caveat: the extension is not  automatically enabled. Log out and then back in. Then you will see the
 extension in Gnome Tweaks, and you can enable it there.

To configure the extension, make sure you have "Gnome Tweaks" installed. In
 Gnome Tweaks, find the extension on the Extensions tab and click the cog
 icon to access the settings.