Easily above average code for Python. I’m going to pick on one method:

def _set_float_icon(self, is_floating: bool):
            """ set the float icon depending on the status of the parent dock widget """
            if is_floating:
                self.float_button.setIcon(self.icon_dock)
            else:
                self.float_button.setIcon(self.icon_float)

First, Python does have ternary expressions so you can

self.float_button.setIcon(self.icon_dock if is_floating else self.icon_float)

Second, what does this code do?

foo._set_float_icon(true)

Kind of surprising that it sets the icon to icon_dock right? There are two easy fixes:

1. Use *, is_floating: bool so you have to name the parameter when you call it.
2. I’d probably rename it to _update_float_icon() or something.

Also use Black or Ruff to auto-format your code (it’s pretty well formatted already but those will still improve it and for zero effort).