In my local jupyter-notebook i can edit mutliple lines of code at the same time: simply press ctrl + click at the respective lines. In google Colab that does not seem to work. I
(In Linux - Chromium, at least)
I managed to do block select but only on contiguous lines, not multi-cursor unfortunately.
Shift+Alt + Up/Down to select multiple lines. Now you can release Alt and use Left/Right to move to the sides. Whatever you do now will affect the whole block.
And, if you select one or more lines with Shift (doesn't need to be the whole content, this affects all the lines with cursor), and then release Shift and press Alt+Up/Down, you will move those lines altogether up/down