No option for opening mutliple tabs in jupyter lab

Hi! I have been trying to open multiple notebooks in separate tabs inside jupyter lab but I could not find any option in the tabs menu. Could you please guide me? Thanks.

You should just be able to open the notebooks and they’ll make new tabs for themselves within the JupyterLab main work area. The Tabs menu is just for keeping track of them and switching between them. (At least in version 2.2.0 that I’m working with right now, see here to try if that isn’t the version you are working in or you want to compare the behavior you are seeing with something else.)
The brilliant thing about them though is you can arrange them side-by-side or above-and-below by clicking and dragging the tabs and dragging and then releasing when the blue box representing the view is the way you want. Plus you have as many option as you want and drag around the borders to adjust and fine-tune. See here for a video demonstrating that.
The other nice thing is if you right-click on an individual notebooks tab, one of the options is to open a new view of the same notebook. And you can place those side-by-side or above-and-below to make it easier to work on different sections of the notebook in conjunction.