Rounded corner in navigation bar

Hi all,

I saw in a public covid19 PowerBI Dashboard (https://www.doh.wa.gov/Emergencies/COVID19/DataDashboard#dashboard)  the use of a navigation bar with rounded edges for the outside buttons and I am wondering how they created this. 

Please find below some screenshots of the behavior when selected:

My try.

How did I create this?

After an extensive online search, I went the creative way. I used one Rounded Rectangle and added two (left corner and right side) rectangle shapes on top of it to cover the rounded edges. On top of all this, I added the button. FYI: I added outlines + transparency to 50% for this explanation.

But this doesn't feel like the best solution, especially because all these shapes will need to be modified on each page.

Anyone a better idea?

Thanks a lot,

Jasper