Question about Arduino Board Libraries

I'm using Arduino IDE V1.8.9

I recently started using other boards (STM32F1 and Wemos D1 Mini)

For each board I use a JSON file in File / Preferences. Specifically



Now my Question; When I copy the NodeMCU json into preference I can select the NodeMCU boards. (I know, obvious)

However when I copy the STM32 JSON to preferences, I can select the STM32 boards but the NodeMCU boards disappear from the board list.

Is this "normal"? For some reason I thought the boards would accumulate, even after the JSON's were removed from preferences.

You need to leave the URLs in File > Preferences > Additional Boards Manager URLs even after installing the package. When you add a new URL, separate the URLs with commas.

Thanks ..... it wasn't obvious.