Keyboard switching from Note editing

I posted this question at the community, but was urged to post here. When I connected a Bluetooth keyboard, an additional onscreen keyboard entitled Android automatically replaced the original Onyx onscreen keyboard. While editing a note, I inadvertently opened a window that let me choose between the Onyx and the Android. Although I can switch from Android to Onyx using a key press after adjusting settings for the Android, I still don’t know what gesture accomplished the change by accident the first time, and I have no way to switch from Onyx to Android other than to go back to the Languages section of overall settings. Can you tell me what gesture or keystroke opens the window for choosing an onscreen keyboard while editing a note? The window actually lists both installed keyboards, and prompts me to make a choice. Thanks.

When you connect to the BT keyboard, please kindly click the keyboard icon at the status bar then you could change the keyboard you like.